I really don't like using nation-names for people, especially if there is no connection. It seems either disrespectful or ultra-nationalist, neither of which is good. It's not just for
Cree, either:
India,
China, Briton/Britain, Ireland...they all kind of make me cringe. There are some exceptions, though- I like
France, as a French version of Frank/Frances etc, and I like
Asia (which as a name may have originated as a variant transcription of
Aisha).