Defaulting on loans helped. When Pennsylvania defaulted on its foreign loans in 1842, one British investor fumed: "There really should be lunatic asylums for nations as well as individuals." He described the U.S. as "a nation with whom no contract can be made, because none will be kept; unstable in the very foundations of social life, deficient in the elements of good faith...." Pennsylvania eventually paid up, but so far as I know, the British Council of Foreign Bondholders is still sending dunning letters to Mississippi, which never repaid its external 19th century debt.
Carl Remick