Proto-Indo-European is estimated to have been spoken no more than 6000 years ago while Clovis culture items are dated about 6000 years before that.
Actually, Pre-Clovis culture existed 20-30.000 years ago, while the Clovis culture appears some 13.500 years ago. At the same time, by the prominent linguists Anton Perdih and Petr Jandáček, Slavophonic Homo Sapiens Sapiens co-existed with Homo Sapiens Neanderthalensis. So, 30.000 years ago what also means that preceded or overlapped with Clovis culture. Not to mention that by same authors, formation of early Proto Slavic language occurred some 70-55.000 years ago.
This just to show you that Proto Slavs qualifies as potential givers of Clovis culture. It doesn`t meant that they give it. Its possibility in the light of opened scientific question in case with eventual `European migration hypothesis` when it comes to origin of north-American cultures and natives.
As for term `Proto-Indo-European`, it is by same authors term that should be replaced in all literature with its more precise synonymous - `Proto-Slavic`.