If the US had not spent so much manpower and treasure to protect Europe, then Europe would have been forced to spend more on its militaries, and less on Socialism.
They would have stuck with socialism, but enforced it like the USSR. And we certainly did not need them rising up as a third power again (like they are trying to do now). Certainly more ought to have been done to suppress the socialist streak in Europe, which is another thing that the US failed at.