All I need is some Aztecs and a Time Machine.
This is a good post. Minor detail, but I think it's worth pointing out that there's a lot of recent-ish research that points towards there being much larger settlements in north America prior to contact. (See 1491 by Charles Mann as just one example, for citations). The running theory is that disease spread out before much exploration let alone settlement had happened in the interior by Europeans- thus, "vast and untrammaled land". 200 years earlier, it looks it may not have been so.