Good point. And there was an element of revenge involved. The Russians had suffered greatly at the hands of Germany and it was felt that it was reasonable to allow them some flexibility.
And at the height of battle of Britain, we gave them 50 destroyers. The RN crews were astounded to find them busting at the seams with warm clothes, blankets, coffee, and foods they had scarcely seen since the war began.
It was an American unofficially flying the PBY that found the Bismarck. US crews flew the planes to England and then “unofficially” become copilots, “training” the Brit crews. An American got the DFC for that mission.
No, America did not leave Britain to struggle on their own. That’s a slander.