Which act banned arms or weapons sales to countries at war forbid loans to countries at war and did not allow Americans to travel on ships belonging to countries at war?

The act you are referring to is the Neutrality Act of 1935. This legislation was designed to prevent the United States from becoming involved in foreign conflicts by banning arms sales, loans, and travel on ships belonging to belligerent nations. It was part of a series of neutrality acts aimed at maintaining American isolationism during the tumultuous years leading up to World War II.