Why did the US support European unity after World War II?

Dr. Samuel Moyn, Chancellor Kent Professor of Law and History at Yale University, says that following World War II, the United States "immediately acted to make sure that the West European countries remain democratic, including through...illicit things like the CIA swinging the Italian election and a famous case. And the European Union comes much later, and really has a much more intra European sources. Lots more people in France and Germany fear what they've experienced, which is two world wars that kind of originate in the clash of these nations, and they want to overcome that, you know, that strife, Americans are, are important, but not all important in the origins of the European Union. And it's really a European story."
This interview is from the FPA archives.