Question

how was the U.S. able to loan billions of dollars to the allies

Answer 1

The Marshall Plan (officially the European Recovery Program, ERP) was the American initiative to aid Europe, in which the United States gave $17 billion (approximately $160 billion in 2014 dollars) in economic support to help rebuild European economies after the end of World War II. The plan was in operation for four years beginning in April 1948. The goals of the United States were to rebuild war-devastated regions, remove trade barriers, modernize industry, and make Europe prosperous again. The phrase "equivalent of the Marshall Plan" is often used to describe a proposed large-scale rescue program.