Roosevelt, the U.S.president who never met a communist or socialist he did not like
, had been chomping at the bit to participate in the war, even before the U.S. was official at war with the axis. This was the only way he could save is so called New Deal scheme, and provide jobs and economic advances for the people he had so skillfully hoodwinked.
The Lend - lease act provided another opportunity to enhance his guided economy, and provide his buddy Stalin with a way to be able to win his part of the war.
Without the help of the U.S.A. , Soviet Russia would have fallen flat on its face.
Just my opinion. (can you tell that I am not an admirer of Mr. R. ? )