"So what is Puerto Rico, if it's not an overseas possession?"
Or Guam, surely thats a colonial anachronistic overseas possession if anything is?
Or how about the so-called "United States Minor Outlying Islands," such as Wake and Midway, most of which had prior claims (usually Spanish) before the USA annexed them?
It would seem the Monroe doctrine opposes European rule of American states, but does not prevent USA rule of Pacific territories closer to Asia than Anerica