General Winifred Scott was bribed by merchants from New York to annex all of Mexico. Scott made clear that he did not approve of this, as it would naturalise millions of beaners, which he did not want mixing with and taking a part in the course of the country's future. So he rejected the bribe—which would be worth millions in today's dollars. and reestablished the border at the Rio Grande, where it was before the fuckers started the war by trying to reclaim Texas.
There is a reason why they don't teach the Mexican-American War in schools.
At cis.org/North/How-About-Wall-Mexico-We-Pay guy pointed out there is an abandoned railroad along this line so it would be incredibly easy to build a wall there. He was proposing that U.S. help fund Mexico building a wall there to keep out non-Mexican illegals.
While that WOULD be good for the US (non-Mexicans are the hardest to deport) the ideal would be if we got Mexican to build a wall along this line (yes, even help them pay for it) and then conquer the top half and drive them south.