Yeah, those types of structures are BC in date, and are obviously culturally linked with similar structures east of the Atlantic. Uniquely in North America they are attributed to glacial action by Denialists. :’) There used to be a huge-lettered inscription carved into some cliff by the sea somewhere in New England, reported during colonial times, but the whole face fell off before photography, only descriptions and maybe a drawing survives.
The most famous is probably Mystery Hill in New Hampshire. That one was attributed to some colonial-era family which lived on the site and built something on top the already extant megalithic structures. Remaining isolationist idiots regard such structures as “colonial root cellars”, which is obviously stupid. One of the Pennsylvania universities did archaeology at Mystery Hill back in the 1990s, and found that a hearth site located *inside* the structure RC dated to 2000 BC.