@milliefink already gave you all the answer you deserve, but just to satisfy any lingering debate…
Because it’s a false equivalency clearly meant to be provocative and elicit an emotional reaction as opposed to a reasoned point of discussion. To wit: The population of North America at the time period this article refers to was racially mixed with approximately 83.8% European heritage 15.6% African, and approximately 1.4% Native N American (though that last number is very fudgy due to a number of factors, mainly racism), while Uganda in the time period you are referencing (now) the racial breakdown is 91% African of various tribal ancestry, 1% European descent and 8% “Other”. The clearly disingenuous falsehood in your logic is that, while the motivations of crime in Uganda may be ethnically motivated, they are not committed en masse by races alien to the region as they were by European-heritage white people against indigenous North American populations. Therefore, it is cogent to the topic to refer to these people as white, yet would be completely irrelevant to a discussion about Ugandan violence. Ya dig?
Most of that talk is based in mainstream history; in a few places, he mentions some less well-accepted theories (regarding Africa, not the Americas), but explicitly flags that he’s doing so as he does.
There is no claim made in that talk regarding American mound-builders.
It may not be questioned by many people south of the Rio Grande, but it is still subject to the same woo as we find north of the border.
Some claim direct links between ancient Egypt and ancient Mesoamerica. Because different civilizations couldn’t possibly come up with pyramids independently, right? It’s all part of the “advanced antediluvian global civilization that They don’t want you to know about” conspiracy, or the ancient aliens conspiracy, and I’m sure someone has figured out how to merge the two grand conspiracies.
Some of this stuff has a pretty good veneer of plausibility, because why wouldn’t it if the people who peddle it (and in some cases actually believe it) spend a lifetime honing their arguments? And some of it lacks even a little veneer.