True, but it is important to know that arrowhead/stone tool styles are VERY consistent in regards to their culture. It's why we even know they could've been European in the first place.
It's possible. My first thought after reading your question was that horses originated in North America, but at some point in the distant past, abandoned the continent for Europe and Asia, and were later reintroduced to NA by the Spanish (iirc). Perhaps there is a link between the exodus of borh the horses and these ancient Euros from North America?
I'll be thinking about this for the next week...