A commonly ignored aspect of the Civil War is the international response to it and the support given to, or withheld from, each side.
Here is one assessment, with further comment in the link.
The American Question Abroad in the Civil War (Part 1)
European attitudes toward the Civil War were destined profoundly to affect its ultimate outcome, yet at the outbreak of the conflict most foreigners were poorly informed about the United States. As Leslie Stephen said in 1865: "The name of America five years ago, called up to the ordinary English mind nothing but a vague cluster of associations, compounded of Mrs. Trollope, Martin Chuzzlewit, and Uncle Tom's Cabin." Influenced by the rabidly pro-Southern London Times, most upper-class Englishmen tended promptly to side with the Confederacy. For years the Old South had been close to Great Britain in both business and society, and it was easy to see in the Southern planters an equivalent of the English gentry. British aristocrats like the Marquis of Lothian, the Marquis of Bath, Lord Robert Cecil, and Lord Wharncliffe thought that the success of the Confederacy would give a much needed check to democracy, both in America and in Europe. More liberal Englishmen, too, could favor the South, supposing its desire to escape Northern "tyranny" was something comparable to the fulfillment of Italian and German national aspirations. The character of the leaders of the Southern Confederacy inspired respect abroad, and the chivalric bearing of Robert E. Lee and Stonewall Jackson enlisted the Englishman's deepest admiration. From the outset of the war, therefore, the "great body of the aristocracy" in England was "anxious to see the United States go to pieces." Though at first not so articulate, there were, in fact, large segments of British opinion which favored the Union cause. Many English manufacturers and shippers had strong commercial ties with the North. The powerful British humanitarian movement, especially the antislavery societies, found it hard to sympathize with the Confederacy. Friends of democracy and proponents of republicanism saw in the United States a model to be cherished. Powerful John Bright, leader of the British radicals, spoke eloquently of the "odious and... blasphemous" attempts of the Confederates to divide the United States and looked to the day when America, with 'One people, and one language, and one law, and one faith," should become "the home of freedom, and a refuge for the oppressed of every race and of every clime." The principal leaders of the British labor movement were "firmly on the side of the North," for they saw in the pro-Southern sympathies of the "millionaire aristocrats, venal politicians, and some of the press, led by the great bully The Times," a "hatred to freedom, jealousy of the growing power of the United States, and a desire to see democratic or republican institutions overthrown or brought into disrepute ." At the outbreak of the war it was far from clear that these latter sentiments, resting on the profound pro-Unionism of the British masses, would triumph. At first it seemed that the North muffed every opportunity to enlist British support. Already fearful of Northern economic competition, which threatened the supremacy of the British merchant marine and challenged the pre-eminence of British manufactures, the English middle classes were alienated when the Republicans adopted the Morrill tariff of 1861. Northern appeals to British idealism were undercut when Seward, early in the war, explicitly declared that the conflict was not being waged over slavery and would not disturb the South's peculiar institution. Even a stanch friend of the Union like the Duke of Argyll was obliged to conclude "that the North is not entitled to claim all the sympathy which belongs to a cause which they do not avow; and which is promoted only as an indirect consequence of a contest which (on their side at least) is waged for other objects, and on other grounds." The English viewed the leaders of the Northern cause with suspicion. Lincoln was an unknown quantity, whom even the friendly Richard Cobden characterized as "a backwoodsman of great sturdy common sense, but . . . unequal to the occasion." It was assumed that the administration would be run by Seward, who was widely distrusted abroad. From careless words spoken during his prewar trip to England he had acquired "a heavy load of obloquy" abroad. Englishmen repeated the story that Seward had boasted to the Duke of Newcastle, during the Prince of Wales's American visit in 1860, of his intention to twist the lion's tail once he assumed high office. When news leaked out of his incredible April 1, 1861, memorandum, proposing to demand categorical explanations from Great Britain, France, and Spain, followed by war against the two latter powers, European fears were confirmed. It was, therefore, with reasonable hope of success that the infant Confederacy looked to Europe for recognition and assistance. A month before the war (March 16, 1861) William L. Yancey, Pierre A. Rost, and A. Dudley Mann were sent on an introductory mission to England, France, Russia, and Belgium. Their instructions from Secretary Toombs were to present to these governments the nature and purposes of the Southern cause, to open diplomatic intercourse, and to "negotiate treaties of friendship, commerce and navigation...." This was the first of a series of diplomatic or commercial missions which, as the war progressed, were sent by the Confederacy not only to the countries mentioned, but to Spain, to the Pope, to the States of the Church, to the United States of Mexico, to the Empire of Mexico, to individual states within Mexico, and to imperial dependencies or dominions such as Canada, Ireland, and various West Indian colonies. In the diplomatic game the enterprising Confederates took the first trick. On May 13, 1861, Queen Victoria issued her proclamation of neutrality, recognizing the Confederates as having belligerent rights. The significance of this initial "concession to the South" is best to be measured by the disappointment it produced at Washington, where Seward asserted that the war was a domestic question and that belligerency should not be accorded the pretended Southern government, as the Washington authorities regarded it. That the Queen's proclamation, a proper one under international law which was imitated in other countries, did involve a recognition of Confederate belligerency, however, was a fact that could not be gainsaid: to the eyes of Europe the government of the South, though not yet a member of the "family of nations," was a responsible government conducting war. As such it was deemed entitled to the rights and subject to the obligations of a belligerent in international law. The matter of status being fundamental, the refusal of Europe to adopt the Northern interpretation of the war as a mere irresponsible insurrection was of real significance; it has even been said that by this recognition of belligerent status "the South almost realized its ambitions of drawing England in upon its side." Fortunately for the Union cause Lincoln had made one of his best appointments for the post at London. Indeed when all the facts are considered it must be admitted that the character and ability of Charles Francis Adams were as valuable as Union military victories in contributing to ultimate success in the war. As a boy be bad witnessed stirring events in Europe; in the company of his mother be bad taken the long and arduous winter journey by carriage from St. Petersburg to Paris to join his father, John Quincy Adams. Passing through the Allied lines, he reached Paris just after Napoleon's return from Elba. After a preliminary education at a drab English boarding school whose master made an unpleasant impression on him, he graduated at Harvard, and studied law under the great Webster. By 186i he had served as legislator in Massachusetts, had become prominent as a leader of the "conscience Whigs" and the Free-Soilers, and had achieved the position of an influential member of the national House of Representatives, where his main contribution was as a moderate Republican earnestly engaged in the work of avoiding war. Though depressed at the nomination of Lincoln, whom he never fully admired, be accepted appointment as minister to England and gave of his best as a loyal servant of the Lincoln administration. "No man in American public life [writes Worthington C. Ford] was by inheritance, training and matured convictions, so well fitted to occupy this office at so delicate and critical a time....Facing perils where a misstep would have involved catastrophe..., he made no mistake... no concession of right or principle."