That other people than American Indians were in the North America a very long time ago is already well established. Spirit Cave Man of Nevada is the oldest known North American mummy at 9400 years and appears to be a Polynesian-Ainu hybrid as does the now famous Kennewick Man (but not before certain Indian tribes and Nordics both claimed him as their own).

http://en.wikipedia.org/wiki/Spirit_Cave_mummy

Then there are the red-haired giants which have been found in many places around the United States. Some of these said to stand in excess of 8 feet.

http://www.helium.com/items/1653360-who-were-the-red-haired-giants-of-early-north-america

http://en.wikipedia.org/wiki/Si-Te-Cah

Sensationalism? Hoaxes? Or is there something to it?

We would have at one time scoffed at the notion of Causasoid red-haired, blue-eyed mummies in China until they were discovered. They are dubbed "Tocharians" and lived about 3000 years ago. The real mystery is, where did they come from? Twin-peaked hats were found in some of the tombs belonging to no known culture.

If the Tocharian mummies had been discovered in America (and who is to say they haven't been?), very little would have been said of it. This leaves the field wide open to kooks who want to talk about Atlanteans and Lemurians and Nephilim from Planet X but the I get the feeling that's how the scholars want it. Weave such a skein of bullshit around it that they don't have to explain it. They can just laugh it off.