The international reaction to the Emancipation Proclamation was an interesting one. On one hand, there was a nearly universal acceptance and congratulations about the moral opposition the United States has voiced against slavery. Nations such as England sent their congratulations about the stance taken. There were some, though, who felt that the Emancipation would hurt the United States' relationship with other nations who were dependent on cotton production, which was greatly facilitated through enslavement. At the same time, some European nations remained skeptical, as they had staked their own national interests based on political party allegiances in America, which could only be sorted out at the end of the war. Yet, the overall reaction to the document was a favorable one, as the United States had begun the process of dismantling a "traditional" institution that other nations either had or would be starting soon enough. The Dutch, for example, had refrained from printing anti- American statements in its newspapers upon the issuing of the Emancipation Proclamation. Overall, the international reaction helped bolster the North's claim that there was a moral imperative to the war with the Emancipation Proclamation.
The war was a precarious balance for the North. Don't give the border states more reason to leave the country, but keep European powers, especially England, out of the war. Get abolitionists off your back in the short term while not actually freeing any slaves in the near term.
The Queen of England was an abolitionist, and I believe this action was the single greatest thing to influence her. She had wept over the book Uncle Tom's Cabin and was torn between acting on behalf of the Empire and its need for cotton, and its desire to divide the potential competitor United States, and her personal feelings about slavery and abolition. The Emancipation Proclamation pushed her off the fence onto the side of staying out of the war altogether.