The US: Mostly anti-Colonialist

In 1823, President Monroe said that the Americas, i.e., the Western Hemisphere, was all American, the European Imperialists had better stay out. The US were not very strong in 1823, but they got stronger and stronger. Spain and Portugal lost most of their Latin American colonies as the US provided Latin American countries with money and weapons to end their status as colonies and become US neo-colonies.

The European Imperialists marched into a country, defeated the military, killed off the rulers, and put a European governor or viceroy as resident Head of State, and with the European Imperialist Head of State as the ultimate Head of State. They also put in a government with all the top officials Europeans.

The US gave money and weapons to a small group so they could overthrow the European Imperialists and make one of themselves the Head of State, with members of the group holding all the senior government positions, and the country was, officially, a free, independent nation. But, if the government did not do everything the US wanted, that government would be overthrown and replaced with a government of Citizens of the country who would do what the US wanted. Meaning (mostly) the US got all the bananas for the cost of good pay for the group forming the government and not much for anyone else, so the overwhelming majority of the citizens of the country were very poor, but the small, select group the US put in to run the country,  all Citizens of the country they were running, got paid fairly well. This is neo-colonialism. No American was in the government, no American was named governor or viceroy or got a senior position in the government, the American agent just told them what they had to do if they wanted to remain as rulers of their own country and get paid very well, i.e., whatever the US told them to do.

The US raged against colonialism for 75 years, but then in 1898, someone told the US President McKinley that every Great Country must have colonies, so the US declared War on Spain and took all the Spanish Colonies and made them US Colonies. They killed off all the colonials who resisted colonialism, and killed, by mistake, people who were not even resisting, but at least no one could say the US was still a minor power because they had no colonies.

The US rapidly decided that it really didn't like Imperialism, and 'freed' the Philippines and Cuba, going back to having them as US neo-colonies, with the governments all native citizens of the Philippines and Cuba (for as long as those governments did whatever the US told them to do).

But then Castro took over Cuba, and got enough support from the USSR that the US did not overthrow the Cuban government, they just embargoed Cuban products. Cuba's economy was mostly selling sugar and cigars, and, since the US was closest, it was easiest to sell just about all the Cuban sugar and cigars to the US. With the US market cut off by Presidents Eisenhower and Kennedy, Cuba had a hard time for a few months, but then the world discovered a cheap source of good sugar and great cigars, and started buying from Cuba until the US put up a blockade (many years later) and pretty much killed the Cuban economy.

(Plus the US uses a US military base in Cuba to imprison all the terror suspects that can't be legally tried in a US mainland court.)

For some reason, the US still has a few colonies, but the grimy details of exactly why they still have colonies when they say they don't want them isn't clear.

In any case, the fierce US antipathy toward Colonialism meant almost all of it ended after WWII, with only a few places still colonies (but lots of places are now neo-colonies, mostly US neo-colonies).