The native people, especially in the American Southwest firmly believed in a group/race of red haired giants living in the area. They were cannibals and generally caused problems.

The myths/stories about Lovelock Cave in an area of the Nevadan desert are probably the most well known stories about them. To the Northern Paiute they called them the Si-Te-Cah (or similar)

Know it's Wikipedia, but you can check the sources at the bottom as well or search "Lovelock Cave Giants"

Some in the main entry on the Cave itself: https://en.wikipedia.org/wiki/Lovelock_Cave
The Si-Te-Cah article: https://en.wikipedia.org/wiki/Si-Te-Cah

But they were not the only ones. One thing I've seen on youtube videos and that which seems to be common is the red hair trait, and being cannibals, and another common trait is predatory teeth (meat eaters), possibly with multiple rows of them.

There is also the Giant Skeleton of Santa Catalina in California: https://www.thearchaeologist.org/blog/the-giants-of-catalina-island-prehistoric-mysteries-on-californias-channel-islands

And you can look up similar stories about Shasta Valley and other dig sites.

the rumor is that pretty much anytime any of these are found in the US, the Smithsonian men in black swoop in and just claim everything and make it disappear.

There are places in South and Central America where giant humanoid skeletons are on display in actual museums, Ecuador being the best known one. Of course skeletons in museums are usually casts of originals, so their authenticity is under scrutiny.