I suspect the original boundaries of Mexican states will be respected in order to not upset the existing elites. Both Sonora and Chihuahua were actual states, not territories while in Mexico. I think there would be a lot of pressure to keep them separate even if they were initially governed as territories and not states.
Baja California might include the San Diego area and other bits of southern California if pro-slavery activists insist on having a potential "slave state" to enter after the rest of California does as a free state. In this scenario, the San Diego area is cleaved off to provide some more population to Baja California. But that is by no means certain. Just speculating.
The New Mexico territory (which included both modern day Arizona and New Mexico states along with bits of Colorado and Nevada) would be like IOTL except no Gadsen Purchase territory south of the Gila River. That would be retained by Sonora. Without the heavily populated area of Tucson and the rest of "Traditional Arizona", I think it is less likely that the western half of the territory will be split off.
IOTL, New Mexico Territory was considered difficult to administer because Santa Fe, the capital, was too distant from the southern portion (cut off by the Jornada del Muerto desert). It's possible that portion will either be retained or given to Chihuahua.
So we might eventually see a New Mexican state that comprises the northern 2/3 of OTL's Arizona and New Mexico, and the Sonora and Chihuahua states that are bigger than OTL's Mexican states. With Baja as its own state (either in its original territorial boundary or an enlarged version with San Diego), then it means a new addition of two states to the Union (since Arizona isn't its own separate state).
IOTL, both Sonora and Chihuhua were heavily influenced by the US. American investors contributed a lot of money to develop ranching and mining. And Mormon settlers (including the Romney family) moved there from 1880-1910 (although this was done to escape US jurisdiction which would not be applicable here). However, given that even Arizona has lots of Mormons I believe they'd expand to Sonora and Chihuahua anyway. So American settlement and investment just becomes more prominent.
I think the additional lands would develop like the rest of the Mexican Cession did. Western style ranching and mining economy mostly, but will become more industrialized in the mid 20th century and lots of population migration once AC is invented.
Overall, not much change for the US IOTL except that there will be larger population of Mexican descent and they will likely make up more of the elite population in those new states than they did in New Mexico, California, Texas, etc. We may also see more prominent ethnic Mexican involvement/leadership in the labor movement given the importance of mining in the these lands.
This will have lots of changes in Mexico though. The Sonoran/Chihuhuan area was important for the Mexican Revolution and produced leaders like Alvaro Obregon, Plutarco Elias Calles, Pascual Orozco, and Pancho Villa. If you remove them from Mexican history, that's a lot of changes. That's two presidents of Mexico alone in that list! And the region was a hot bed for anti-Diaz movement and essential for the victory of Francisco Madero in the first stage of the Mexican Revolution. Huge butterflies here.