Catton indicates that the vast majority of the world powers at the time were either ambivalent or adopting a wait and see response... This European powers in particular could afford thanks to bumper cotton crops - the political leverage the South believed they had in withholding cotton exports was thus far less effective in promoting their agenda than they'd hoped.... Indeed Catton concludes that southern diplomacy was generally a failure.

This is not to say that European powers held an opinion of the Union that was always positive. The Union's blockade combined with the UK's rather unapologetic construction of ships for the CSA caused significant diplomatic incidents but these never really looked like eventuating into war. Indeed Britain made quick reparations for political and economic damaged caused after the war concluded, so the relationship was not as antagonistic as their recently shared history would've otherwise suggested.

The Russian Fleet wintered in California during the war, which served as a morale boost to Union citizens, although the stay had more to do with Russian pacific interests than altruistic aid.

After Lee's defeat at Gettysburg it became clear that European recognition would not be forthcoming, and from there it was a matter of time and if, as Foote famously suggested, the Union would decide to "bring its other arm out from behind it's back".