The short answer is yes. Had we not, the Nazis might well have forced the Russians into a stalemate east of the Urals and the Brits likely could not have invaded the continent alone.This all might have proved disastrous, as Germany was well on its way to developing a nuclear program, and had the most advanced rocket scientists in the world at the time. In fact, most of the most prominent US rocket scientists from the 1950's and 1960's were Germans who had risked their lives to cross Germany in a commandeered train in order to surrender to US forces and avoid capture by the Soviets.The "cold war" may have been us against a Europe dominated by Nazi Germany. The difference was that the Nazi's ideoplogy was that they were "racially" superior and deserved to rule the world. The Soviets feared us more than we feared them. Nuclear war may well have resulted from such a situation.And while the Germans didn't have much of a Navy in 1941, imagine if they had pacified the Russians what they could have built, all the while the US remaining neutral and not gearing up for war. The US east coast has never been fortified and Hitler most certainly had plans for war with the US once he disposed of his other enemies.