If that could be considered an invasion, at least it was an invasion by invitation.
When the Europeans realized that the Treaty of Brussels, signed in 1948 by Belgium, the Netherlands, Luxembourg, France, and the United Kingdom, did not provide the military power needed to protect them from the Soviet Union, they began an active recruitment effort to bring the United States into their fold. This resulted in the North Atlantic Treaty which was signed the following year.
France eventually objected to being dependant on the US and withdrew from the alliance. I vividly remember Charles DeGaulle asking the United States military to leave France in 1966. We may be the only "invaders" in history that when asked to leave, simply did!
That was a win/win for him, he got to show his resolve and independence to his countrymen while knowing that France would remain under the protective umbrella that we extended over his neighbors. A brilliant move actually.
The rest of the European alliance has continued to depend upon NATO for their primary defense, seemingly gladly accepting the invited US presence in their countries. I wonder what would happen if the US backed out of their NATO commitment, which would then require the remaining European countries to fill the void?
Personally, I think it may be time to find out, especially if our purpose there has been forgotten by the locals and we're seen in the light of an invader rather than as an invited presence. It would certainly help our national debt as well.