And what great strategic threat did a victorious Germany actually represent to United States interests that the US was willing to undertake a war across the Atlantic which it knew would be massively costly in blood and treasure?
For that matter, what reasons beyond benevolence did the United States have for aiding Britain and France with programs like Lend-Lease before its entrance into the war?
Hitler's immediate aim was dominance of the continent; however, once this had been achieved, it us unlikely that Germany would have tolerated the United States as a rival for 'weltmacht', or world power. Between the u-boat menace, the German naval plan Z, and other potential threats (ie Amerika Bomber project, German nuclear programme), even if the United States did not face an immediate threat, it was a threat that would rear it's very ugly head in the future.
There were also distinct fears that the Germans would attempt to influence Latin America, such as Juan Peron's Novo Estado in Argentina. There were various American war plans for intervention, in Brazil as one example, to head off Nazi attempts to carve out a sphere of influence.
Hence the lend lease program. By strengthening Germany's enemies, the united States could prevent the need for intervention, unlike in WWI. This proved not to be the case however, and involvement in a second, more terrible world war would be required.
That answer your question?