>>4939298
The Mexican War started because the treaty set the border with Texas as the Rio Grande after it won independence but when it joined the union the Mexicans said Rio Grande just meant "big river" and was the Nueces.
We said bust the deal face the wheel sent troops over the Nueces and war started.
The Mexicans were not going to keep Norte California no matter what. Even the Brits and the Russians had eyes on it.
Regarding New Mexico, Arizona etc. they might have had it on the map but it was really the Comanches who owned it. When the Comanches got bored they raid Mexico proper for slaves.