What I'm thinking is Morelos survives the revolution, Santa Anna dies bravely in the struggle for independence, and Augustine I dies in obscurity. While the new Mexican Republic is certainly not going to be perfect, and there is going to be a lot of economic difficulty, inequality, and corruption to deal with, it also at least has a chance to work through these issues and maintain stability. I want to take the reasonably optimistic view, and say the Republic was moderately successful in these endeavors. A quarter century down the line, however, and war with America is looming. A rebellion was quashed in Texas a little while back, and the Army, while not world class or chock full of genius generals, isn't Santa Anna's plaything, either.
What I'm wondering is whether a better led Mexican Army under a stable republic can possibly give the United States problems in a war. I'd think that if the Mexicans stay on the defensive and fight bitterly, and these soldiers are reasonably well led, America may end up bogged down. If Mexico can keep that up long enough, perhaps eventually the Americans could be forced to withdraw/negotiate. Manifest Destiny didn't have overwhelming support, so a foreign adventure that seems to be going nowhere and is costing a lot of money and lives could get to be unpopular stateside, and eventually the population may elect someone against such adventures, bringing an end to the conflict.
Does anyone want to bolster or tear down my uninformed navel gazing?