There are interesting mounds around the southern and eastern U.S. also, from several mound-building cultures. And there seem to be the same kinds of mythic stories of treasure. Though in the Choctaw (mostly in Mississippi) case, they are known to be bone houses, based on some particular practices of dealing with the dead. (Placed on platforms to rot, then the bones picked clean and put in a basket in storage until there are enough accumulated to build or add onto a mound to bury them.)

There may also be some in Mexico and the U.S. Southwest, though there we hear more about the ball courts and mud houses than mounds.

SRS