Perhaps we have different definitions of colonies then, because I think the answer there is obvious: Canada isn't a colony of the UK any longer and hasn't been since 1931 or 1982 depending on which event you want to use. Just like Afghanistan, Armenia and Romania aren't colonies of the US, even if we've set up puppet governments [1] in those countries. There's a great deal you can rightly criticize about US foreign policy post-WW2, but calling us modern colonizers doesn't fit.

[1] I don't know enough about the events you're referencing in Armenia and Romania, but Afghanistan was war. Of course we were going to set up a government that was friendly to the US.