[notfromhere]

"America" is a place name created by Europeans and "Americans" an identity created by their descendants.

So there's no "ethnic" Americans because its an invented social identity.

[carlosjobim]

No, the landmass physically exists and people existed there before European discovery, no matter what you call the place. They were and are the native people of America - hence the "Americans". As opposed to the people who came there recently from Europe, Asia and Africa mainly.