I have been on a Civil War reading binge lately, which began when I read "Time on the Cross", which is a really interesting economic analysis of American slavery. Since I have read a number of other Civil War and Ante-Bellum history books, including James McPherson's excellent one volume Civil War history.
I was struck in several of these books by the reaction of British textile manufacturers to the war and, more specifically, the informal southern embargo of cotton exports in 1860-61. These textile producers screamed bloody murder to the British government, demanding that they recognize the Confederacy and intervene on their behalf, claiming that the lack of cotton would doom their industry and thereby doom the whole country. On its face, this was a credible argument, as textiles probably made up more of the British GDP at the time than any three or four industries account for in the US today.
Fortunately, the British chose not to intervene, and risked the economic consequences of not supporting the textile industry by jumping into the American Civil War. As it turned out, the British economy was fine, and in fact even the textile industry was fine as well, as demand was still high and other sources around the world stepped up (because of the higher prices that resulted from the Southern boycott) with increased cotton supplies.