Here are love letters that i found

 “On the United States side, the British fostering of and of support of the Confederacy, and their well-known plans, pending successful outcome of the secession, to further fragment and subdivide the Union, need no elaboration.”

Konstantin George wrote in his article “The US-Russian Entente that Saved the Union," (Konstantin George “The US-Russian Entente that Saved the Union, ”The Campaigner Vo1.11 No.5 July1978) In a separate article he wrote, "The cornerstone of Britain’s operational policy, from no later than 1860 on, was to dismember both the United States and Russia."(https://hwaairfan.wordpress.com/2015/04/25/american-civil-war-when-russia-blocked-british-led-intervention-against-the-union/) The New York times article "Our Visit to Richmond," August 15,1864  states the the reporter J. R. GILMORE saying

"... we think Union essential to peace...could two people, with the same language separated by only an imaginary line, live at peace with each other? Would not disputes constantly arise, and cause almost constant war between them?"

English Canadians speak the same language as Americans.
The Southern Revolution of 1861 was caused by English interference in the South as well as causing a revolution in Poland.The secession documents of certain states (It is not true for all ) use wording that is only in England that is inconsistent with the area that seceded such as "African race."  ( This puts Afrikaaners into the same race who are clearly white.)  The bigest proof is from thw article "American Civil War viewpoints: It was British arms that sustained the Confederacy" by Peter Tsouras which states the best confermation because Confederate ammo boxes had UK Royal seals on them.
 The United Kingdom was the weapon supplier of the Confederacy, allowed the colony of Ireland officially support the Confederacy and the Confederacy to raid from Canada on Maine, was in the "Great Race" cold war against the US, made up 90% of the confederate fleet, gave their greatest weapon to  be manufactured in the South and had a large population vocally supporting the CSA with a distant possibility that Jefferson Davis may have been an agent for England as  there was evidence of his hidden correspondence with England but Judah Benjimin has a better chance of being the British agent as he was born and died in the UK and burned all official Uk-CSA and confederate spieing documents. (The South inspired Canadian Confederation. also the English intervention in Poland will not be looked into here) Allen Salisbury wrote in his ground-breaking book The Civil War and the American System, the War of American Aggression "was the second military phase of the political battle which raged between Britain and the United States from the time a formal ceasefire was concluded at Yorktown in 1781."

The other reason for British interference was also simply British conquest of America. England wanted to recoup what she lost in in the American. It was planning to make the British Dominion of the South out of Dixie. Judah Benjamin sent a letter to the British Counsel in New York that said this:

Sooner than yield...we will upon certain conditions, at once return our allegiance to Great Britain, our Mother Country. Many, very many of the most wealthy and influential planters though out the South have already discussed this alternative, in the event of the election of Mr. Lincoln, and the popularity of the proposition seems to pass from one to another almost with elastic rapidity... My chief object is in approaching you is to cultivate your friendship, and procuring your cooperation in aid of accomplishing this great object of returning to the dominion of our fathers' Kingdom" [T. Weed & others, The Life of Thurlow Weed, 2vol., Boston, 1883-84, v II, pp 313-14]       

Allan Nevins states this in a chapter of his 1960 “War for the Union” as, “No battle, not Gettysburg, not the Wilderness, was more important than the context waged in the diplomatic arena and the forum of public opinion. The popular conception of this contest is at some points erroneous, and at a few grossly fallacious…” In William Jones' article "Britain's Surrogate War Against the Union, 1861-65" it states,"What the British really wanted was not a direct conflict with the United States—that might well end up costing them Canada—but rather to make the split in the Union a permanent one." Albert Woldman wrote in his book "Lincoln and
 the Russians" that England had to crush unified America to "weaken a dangerous commercial competitor, removea barrier for the advancement of England’s interests in the Western Hemisphere, and free a source of cotton supply.” (Woldman, 84.)

As early as a letter on April 13, 1854 from the US Mintser to Russia T.H.  Seymour to thee secretary of State ``the danger is that the Western powers of Europe ... after they have humbled the Czar, will domineer the rest of Europe, and thus have the leisure to turn their attention to American affairs.''  Anton Chaitkin's book Treason in America, from Aaron Burr to Averell Harriman goes more in depth on England starting the war.
Al Palladin said in his speech "Russia's participation in the U.S. Civil War – the diplomatic and military support that saved the Union" to th Olympic club on February 2, 2017, "If only there was an opportunity to reshape the balance in the North and push the U.S. back… The American Civil War was deemed by many in London as an ample chance."
The United States knew that had caused the war was England as American Minister of the American legislation in England George Marshal told Secretary of State Seward on April 9,1861:

"[England] cannot be expected to appreciate the weakness, [apart from weak against England] discredit, complications, and dangers which we instinctively and justly ascribe to disunion, English opinion tends rather, I apprehend, to the theory that a separation may work beneficially both for the groups of states and not injuriously affect the rest of the world." MPUS, no. 330, Dallas to Seward, April 9, 1861. 

Seward the same year demanded a direct war on England recognizing England as surly responsible for the war to which Lincoln responded famously "One war at a time!" Richard Franklin Bensel wrote on this in his book Yankee Leviathan: The Origins of Central State Authority in America, 1859-1877 say that Seward’s proposal “revealed the new secretary of state’s profound awareness of the narrow basis of northern nationalism during the early months of the Lincoln administration.” Even so September 5, 1863, Secretary Adams told the UK's Foreign Secretary John Russell, “It would be superfluous in me to point out to your Lordship that this is war.” (Crook The North, the South, and the Powers 1861-1865 pg. 324, 326)

This idea was even pointed out in the film "National Treasure II" (U.S. Civil War: The US-Russian Alliance that Saved the Union by Webster G. Tarpley  for Voltaire Network proves the pemesis of the film.) recognizing the fact that Queen Victoria sought to intervene for the Confederacy even as the seven cities of Cabecobila being fiction with "Harper’s Weekly"  on Sept. 24, 1863 stated “England and France have shown themselves to be unfriendly powers.” The reason for this is simple to defend Canada and French colonies (As Seward kept annex it) from the US, prevent the country from supporting the revolutions in Erin as Fort Erie (Ontario) fell to American veterans in 1866 only for the United States Government to back track, could not accept a new North American empire and stop the international slave trade that the US was considering reopening; and Secretary Seward kept trying to annex Canada. . Russian Ambassador to London Baron de Brunow told Moscow January 1, 1861:

"The English government, at the bottom of its heart, desired the separation of North America into two republics, which will watch each other jealously and counterbalance one the other. Then England, on terms of peace and commerce with both, would have nothing to fear from either; for she would dominate them, restraining them by their rival ambitions."" Dean B. Mahin, One War at a Time: The International Dimensions of the American Civil War, (WashingtonD.C.: Brassey’s, 1999), 24.

However the question of slaveries connection to the war is still active as the British Empire had outlawed Chattel Slaver but other types were active, the Constitution of United States guaranteed the right to Chattel slavery. Roger K. Broxton of Andalusia, president of the Confederate Heritage Fund said,

"There is no proof of Lincoln ever declaring the war was fought to abolish slavery, and without such an official statement, the war-over-slavery teaching remains a complete lie and offensive hate speech that divides Americans, as is being done now by the media and politicians regarding the Confederate flag in South Carolina." (https://www.al.com/opinion/index.ssf/2015/06/war-over-slavery_rhetoric_is_i.html retrived Februar 14, 2019)

Like wise, the highest persentage of slave owners were black .(10% to 15% aginst anglo 4%) Lincoln was a supporter of Imperial slavery as in the United Kingdom even becoming an ally of the Russian Empire. (Alaska was sold to the US to buy off Seward.)
American Ambassador Clase wrote Lincoln in July 1861, "“I told the Emperor we did not care what England did, that her interference would tend to unite us the more.”
In answering the question of this idea of British causing it as "stupid." This needs to be remembered that the British did the same in Poland at the same time and Germany did this to Russia to cause Russia to surrender in World War I. To answer the Question of slavery, one only need to be remembered that Texas as a state of the Mexican United States exchange slavery with indentured servitude, and the "Jim Crow" was the as response to Reconstruction. South responded with contracted share cropping in which the breach of contact in the South is a matter of Criminal Law currently in the South. The Idea that the Revolution of American Aggression was foremost bound to Lincoln's biographers of his cabinet to hide Lincoln's mental illness and other failures in the presidency.

However, the revolution in its entirety was and to a lesser extent anti-government expression. It was a popular uprising as all races in the CSA were supportive of secession. As the CSA never truly had a truly unified government, the unifying principle was a war against federalism drawing in even Christian Anarchist such as Mennonite into arms. The Government of the US responded to this American "Rusifation" called "Sermn's March to the Sea" and "Reconstuction." With this, American expressed its true nature as federal soldiers frequently raped Sothern Belles and murdering as the US national Anthem states "conquer We must." The extent of the war was by no mean different then the Philippines’ or San Juan revolutions save for an English start.

 The War was a popular uprising which, according to the book The End of Tsarist Russia by Domic Lieven states that 30% of the general population of all races in the Confederate States of America served in their armed forces garnering more general support than the American Revolution only falling due to the despotic nature of American "nation burning" to the extent of creating the idea of the American Empire while making it too weak and endangering Russian Alaska.
 The other question is about "white supremacy." The war did show English superiority as Americans were killing each other and that the Russian Navy not American victory in the Battlefield of Appomattox. Ironically Both the US president and the Czar both were assassinated. )However according  to the end of Amanda Foremans' book A World on Fire, the United States forced England to pay facial retribution for cause the war in the 1870's.