> Obviously there were native Americans here long before European settlement, but evidence of their presence has been so thoroughly erased
Most of what the native Americans built would be erased by now anyway. They mostly didn't build with stone or metals, but with wood that rots. Most European castles were built out of wood and there is not trace remaining other than town archives (if that) even though no deliberate effort was made to erase them.
Not to excuse the deliberate eraser of history, it happened and is bad. However don't get the wrong impression either, most wasn't deliberate history erasing. Most of it was natural decay, followed by this useless bit is in the way of progress - the natives did exactly the same thing to their old worn out structures.
I live in wiltshire, in the UK. There are lots of ancient hill forts. They were originally terraced earth + wooden pallisades + wood/mud buildings. All the wooden structures have long since decayed, but the earth structures still remain, if somewhat eroded. I guess there isn't much in the way of hills on the American plains though.
America is a lot bigger than the uk - it extends across the whole continent. so all gereraizations are false on some level. There are places where the natives left hills (mound buildres). However in general they were not building that way: wood is a lot easier to build withe than earth and usually good enough.
Most of what the native Americans built would be erased by now anyway. They mostly didn't build with stone or metals, but with wood that rots. Most European castles were built out of wood and there is not trace remaining other than town archives (if that) even though no deliberate effort was made to erase them.
Not to excuse the deliberate eraser of history, it happened and is bad. However don't get the wrong impression either, most wasn't deliberate history erasing. Most of it was natural decay, followed by this useless bit is in the way of progress - the natives did exactly the same thing to their old worn out structures.