Unless I'm missing something, it seems as if this represents one group of early Americans, not necessarily the first.
And from the article fromwhich blam bolded the following sentence:
Comparing the DNA found in the tooth with that sampled from 3,500 Native Americans, researchers discovered that only one percent of modern tribal members have genetic patterns that matched the prehistoric sample.
You are not missing anything--you are correct, a point that the writer of the piece either did not understand or left out purposefully.
There were several peopling events that occurred in North and South America. This data shows one that happened 15k years ago--no more, no less.
And thanks for posting, blam, and thanks for the ping, SC.