World War II was total war! We sure as hell would have dropped atomics on Germany.
The preparations for the invasion of Honshu were because at that time we did not know if the bombs would work. We had tested one U235 bomb at White Sands, New Mexico. Therefore, we knew the one we dropped on Hiroshima would work. As mentioned U235 was in critically short supply. The production pipeline for coming bombs was mostly plutonium. The first test of a Plutonium bomb was when we dropped it on Nagasaki. It worked, its yield was actually greater than the predictions. We then knew we could start turning out workable atomic weapons on a large scale.
An irony of history is the work of German and East European Jewish Scientists. They fled to the United States because of persecution and worse by Hitler. Those German Jews were loyal German citizens. In effect Hitler gave us the bomb by driving out these brilliant scientists. They would have built the bomb for Hitler as loyal Germans if Hitler had not persecuted them.
The Trinity test was of a plutonium device. There were no doubts about the U-235 bomb. But there were questions about the plutonium approach.