Mexico had only 1/3 of the US's population in 1848. Sure its 19th century rate of population growth woudl be larger than our timeline but you forget that mexico would be in a first world nation so it wouldn't grow as much as it did in our 21st century(instead of 110 million mexicans plus 20 million more in the US making 130 mexicans we'd see abotu 1/2 of that). We'd have about 70 million mexican-americans in that timeline. Thanks to air conditioning/demand for labor we'd see mexicans move north like how the blacks did so only about 30-40 million mexicans in the mexican states
