The thirteen colonies were only a small part of what made up the United States. Anyone else was not counted in the Census which is basically 80% of the rest of what became the USA. And the many of the people in that 80% were wiped out by disease, warfare, etc...

Basically, the Americans conquered the whole country. Its like the French declaring anything west of the Mississipi theirs. What happened to the people living there? I bet they didn't say, yes France, you own us.