Kennewick man is not yet completely investigated, but the 'Caucasian' interpretation is rejected.

This paper from the AAAS (American Association for the Advancement of Science) explains how a native group is thwarting studies.
Kennewick man controversy

I understand that the remains have not yet been released for additional study and are still the subject of Court actions. Without further peer and controlled laboratory studies, the studies linked below are the best available.

The conclusions of one investigative team, Powell and Rose, 1999, Chapter 2 of the National Park Service summary of results, are:
The age assigned is accepted (see results of the radiologic team).
There is no study of native Americans showing changes from c. 9000 years ago to c. 1000 years ago, so the relationship postulated by the tribes (and the radiologic team) cannot be verified.
The bones suggest relations to the earliest Americans studied (remains from the Great Basin), the Ainu, and southeast Asian remains.
There is nothing to suggest relationships to 'caucasoids' from Europe.

No reliable DNA results were obtained (Chapter 5)- fossilization and contamination defeat current procedures.

The National Parks Service Archaeology Program on the remains:
Kennewick Man