People getting wise to the military. Many would defend their country, but don't want to die for an oil company to make an extra thousand. Guessing which is more likely is left as an exercise for the reader.
And the good thing is you'll have plenty of warning because your government is unlikely to join the war against the nazis for a good couple of years into the war against the nazis.
I jest....but kinda not really given current US foreign policy (or that of the past 100yrs tbh)