Battle of the Alamo... another rag-tag group manages to defend a crumbling old mission against a force of thousands inflicting massive casulties upon the Mexican army. Even though they had siege cannons nearby that could have taken down the walls without an assault. No way!
Battle of San Jacinto... the Mexicans have the rebel army trapped and what do they do? They decide to take a nap without even posting sentries, thus allowing the band of Texan rebels to crush them soundly in the space of twenty minutes. Silk underwear even become a major turning point in the battle as this proves they captured the Mexican president! ASB!
After losing that war to the rebels, and adamantly refusing to admit their independence, Mexico waits to launch a major invasion to reconquer Texas until AFTER the major power on the continent annexes them and thus gives the land-grabbing US a chance to grab all of Norte Mexico. ASB they'd be that dumb!
Sorry but that is a huge over simplification of the Mexican American war., very much based on American-sided elementary school level text books.
For one the Texians didn't hold on to the Alamo, they were all massacred. Inflicting that much damage to the attacking army when you have the upper ground and a well defended position isn't that ASB, even when you're defense doomed since the start.
San Jacinto and the "nap" was very good luck for Houston and his men but they still had the field advantage, they basically got to choose the battleground. That Santa Anna decided to wait only helped them but it was certainly not decisive.
Mexico never launched and invasion to re conquer Tejas. The whole "American blood on American soil" was propaganda by the Polk administration to gain support from Congress for the war. Mexico, when Paredes was in power, did send a large army across the Rio Grande to defend the Nueces Strip, which was technically part of the department of Tamualipas and not Texas or the US, after Taylor had moved his troops south of the Nueces and stationed them near Matamoros to claim the strip for Texas/the US. The declaration of war Paredes sent to the US for annexing Texas was never actually ratified by the Mexican Congress so technically it was more of an very angry letter from Paredes to Polk than an actual declaration of war.
The real ASB part of the Mexican American war is the life of Santa Anna. You basically have the most inept military commander in military history coming in and out of power in Mexico 11 times in a period of about 30 years or so. Even after being exiled twice out of the country. Not to mentioned the fact that his longest right happened after loosing the war against the United States and being exiled for the second time.