Yesterday I visited Serpent Mound in Peebles, OH. There are not many truly ancient constructions still visible within the United States, but this one dates to about 300 B.C., is relatively nearby, and the head of the snake and several coils appear to be aligned with astronomically important directions, as signs at the site indicate.
These combine to make this perhaps the best local counterpart to Stonehenge.
The precise significance of Serpent Mound to its builders, or for that matter to later people who lived in the area, is not entirely clear. Think of all the migrations that have taken place in Europe since 300 B.C.; well, people in the Americas moved around, too. Likewise, since 300 B.C. Europe has seen not only the various pagan traditions that were present at the time, but also Christianity (with significant developments like the Protestant Reformation), Islam (particularly in the Iberian Peninsula and southeastern Europe, Mithraism, and Gnosticism, and these various religions frequently used the same symbols to illustrate different ideas. Even within the superficially stable area of Egyptian polytheism, there were important changes from pre-dynastic Egypt to the banning of polytheism in favor of Christianity. Again, the native inhabitants of North America must likewise have had dynamic religions, only they left no written record. It is safe to say, though, that what American Indians believe today is not identical to what they believed in 1492, and what they believed in 1492 was not the same as what they believed in 300 B.C.
Although we do not share all the beliefs of the people who created Serpent Mound, it is widely accepted that we should respect the monuments for historical reasons. Not everyone does this, of course. In 2001, the Taliban dynamited the "Buddhas of Bamiyan" because they did not agree with the ideas represented by those statues. More recently, ISIS has destroyed countless buildings, statues, and artifacts (to say nothing of people) that represent ideas with which they disagree. And, in much the same vein, it has become fashionable for universities and cities to remove Confederate monuments that have stood for decades, or even for over a century. No one (except, perhaps, a Buddhist) who approves of that has any solid basis for condemning the Taliban for destroying the Buddhist statues.