[Eltabaco]

After the French pulled out of Vietnam the US took over as colonial power du jour. It was the same colonial game that had been played by the French, British, Germans, Dutch, Spanish, Italians, and Portuguese for centuries, only with newer players-- the Russians and the US-- and instead of colonies, possessions were called "spheres of influence". There's a fort in San Juan, Puerto Rico that I believe had been taken and occupied by the French, Spanish, and British all within one year, but after the US started playing the colonial game in earnest with the Spanish-American War, it became a possession of the US.
But, actually, despite what your 5th grade teacher said, the US began playing the colonial game early on, and was never the peaceful "non-interventionist" nation we were told it was. In 1812 when the Brits were busy fighting the French, southern "War Hawks" in the US Senate orchestrated an invasion of Canada which failed. The Battle that Saved Canada - The Friends of Crysler's Farm Battlefield Memorial