The US rebuilt the economies of its former enemies after WWII — on purpose

Between 1948 and the mid-1950s, the United States gave over $13 billion — well over $150 billion today — to help rebuild Western European economies, including those of Germany and Italy, which it had just finished fighting. The plan aimed to head off the economic collapse and instability that had helped fuel the previous war. Historians credit it as a major factor in Western Europe's rapid postwar recovery.

— US Department of State, Marshall Plan — European Recovery Program, 1948-1952