The more I look at the Mexican-American war, the more I realize how kind of one sided it was. America had better technology, more morale, and much better military minds. Really, I don't see at all hoe Mexico could have won at all, but maybe I'm missing something. Did Mexico have something that might have tipped the odds and let them win?
It's worth remembering that the Mexican-American war was not a war with only two sides. It's more accurate to think of the war as a civil war in Mexico that happened to involve the US.
We have to ask what it would have meant for Mexico to have "won". The independence of Texas was a forgone conclusion by the time the US entered the war, but California and New Mexico were not. Had General Kearny not been reinforced by Cmdre Stockton or the Californios had more men, perhaps California might have been lost. Had Santa Fe put up a fight against Americans in the early war and been properly equipped by Mexico, they might have prevented Kearny from reaching California entirely and kept their own independence.
Sadly, AskHistorians is not the place for What If questions. We can't really ask how things might have been different without speculating. It is worth noting that the Mexican-American war was not an unequivocal loss for Mexico, despite how it's treated in textbooks. Mexico prevented the US from obtaining land on the Gulf of California and made Apache raids an American problem rather than a Mexican one. At the same time they ended the long-running independence of the Yucatan Republic and centralized power in the federal government.