Agreed. The United States may own the territories won from Mexico for now, but should this country ever find itself at the mercy of a group of other countries, one demand is certain: Mexico will step in and demand the return of these "lost provinces."
They lost a war and they sold the land we bought for lots of money on those days, including lots of Mexican international debt we took over as well.
We also did not displace prior Mexicans from their lands, we assimilated them into the culture and they were protected from what I read.