The US contribution was welcomed by the allies in both wars. American sacrifices were enormous, their valour admirable, your word intervene close to fact: "come in as something extraneous, occur in the meantime"---Oxford English Dictionary. Isolationist in policy, the US was torpedoed into the First and bombed into the Second, its bunds and seig heils clamouring as the British Commonwealth and allies fought fascism alone. The West also benefitted immensely from the Soviet Union's sacrifices, surpassingly higher than any other country, our Western Front a comparative sideshow to the Soviet sweep from Moscow to Berlin.