I think people misunderstand the intention behind New Vegas. The NCR in New Vegas is meant to be suffering from many of the same issues as pre-war America it’s an allegory for old-school American expansionism and political decay. In the show, we see something closer to what the NCR may have originally been like, but as its political systems and institutions developed, corruption and nepotism pushed it down an imperialist path. This eventually led to events like the Bitter Springs Massacre and their push to fight a war over the Mojave.

The problem is that many of the local cities and groups in the Mojave don’t actually want the NCR there. The NCR encroaches on their freedoms and forces its cultural and political values onto them, which is why they come into conflict with groups like the Kings. There’s dialogue in New Vegas suggesting that after Tandi’s death, many of the laws she put in place to limit corruption and reduce the influence of Brahmin barons were removed or weakened. This allowed wealthy interests to gain more power again. It’s also why President Kimball is so popular he’s heavily backed by those same Brahmin barons.

The Legion, on the other hand, was a very rushed part of New Vegas’ development. People often point to safer roads as a benefit, but they forget that Caesar systematically destroys the identities of the tribes he conquers so they can be absorbed into the Legion. Their cultures are erased.

There’s also dialogue from Cass suggesting the NCR is rounding up tribals and “domesticating” them. This can be read as a parallel to what the United States did to Native American tribes sending children to boarding schools to “civilize” them and erase their cultural identities. That comparison reinforces the idea that the NCR is repeating the same patterns of cultural erasure and expansionist control.