Yes, the US ws a colonizer, although I will be the first to admit it was a relatively benign one. In Puerto Rico, in spite of self-government, the US handles the post, customs, passports, federal courts, and all international affairs, and federal law and regulation is in effect. I worked there for the US Atomic Energy Commission. Puerto Ricans do not vote for President and they are subject to the draft in wartime. It is an arrangement the Puerto Rican people have ratified at least twice, by plebescite. I lived in PR for a year, so I got to talk to a lot of people about it.

In Cuba, American troops were stationed in Cuba til into the twentieth century, well after the Spaniards were kicked out. I know this because my grandfather and his family were helped by a kind American soldier when he was 5 (he was born in 1898) and he told me the story himself. It is a story I have posted here before. The US secured permanent coaling rights for its fleet in Cuba, got long term access to its Navy base at Guantanamo, and through the Platt Amendment, reserved the right to interfere in Cuban affairs. There was even an American administrator present. The Platt Amendment was repealed during, or shortly after WWII. As in Puerto Rico, American engineering and public works were a vital part of the infrastructure.

The Phillippine Islands were the most colonial of the three former Spanish possessions; in fact, the US fought a guerilla insurrection there for years. Although the Phillipines were freed after WWII, we still maintain a formidable military presence and strong economic ties. When I was in the Phillippines in the 60s I was struck by how pro_American the people I met were.

In addition, the US forcibly occupied Hawaii to support the interests of US planters there, and annexed about half of Mexico in a forced sale after the trumped-up Mexican war of the 1840s, perhaps our most brutal colonial exercise, if you don't count our own aboriginal peoples. There are also numerous small Pacific isalnd holdings, each with its own history, of which I am mostly ignorant. These are the official colonies, I will not mention the de facto colonies where the influence is strictly economic, providing the government remains friendly. Panama was actually created by the US so we could build our canal there. The history of the US Marine Corps in the Carribbean will help locate these quasi-colonies.

The US cannot match the Europeans in the length, extent or brutality of its colonialism, but it most definitely was a colonial power.