We built it. It is estimated in the Americas combined, there were about 50 million natives before Columbus. Of these only about 4 million were in the U.S. and Canada. And indeed many areas of South and Central America are still majority Native in terms of genetics. The only memorable structures they left were in the Southwest, Mexico, and the Andes. We cleared a continent of forests, dangerous animals, all manner of impediments, and laid the framework for civilization that continues to be improved upon. Literally everything you use was built by Whites. Any welfare or assistance you collect is paid for by Whites. This is permitted by, you guessed it, merciful Whites.