What often isn't explored in scenarios where the Texians lose at San Jacinto is that General Pendleton Gaines was in Louisiana on the east bank of the Sabine river with the 6th US infantry and some number of dragoons. He had given a wink and a nod to "desertions" for some of the volunteers in the Texas army. The border between Texas and the US was not clearly defined. Had Santa Anna continued eastward, there's legitimate speculation whether that would have triggered a response from the US Army, ostensibly to safeguard the thousands of Americans caught up in the runaway scrape, as Gaines' order was to protect the border's tranquility from Indian attacks.
There's this little gem, which I found on ancestry dot com. At the moment, I don't know if it actually matches the reality of the situation, but it wouldn't surprise me if there was more to Gaines' proximity to the border than simply "protecting the tranquility of the border".
Francis T. Duffau, for example, a member of John A. Quitman'sqv company of Mississippi volunteers, claimed to have had documentary proof that President Andrew Jackson had assured Sam Houston that if the Mexican army were to cross the Trinity River, Gaines and his army would come to the Texans' aid. Historian Henderson Yoakum wrote that Gaines ordered Col. William Whistler and elements of the Seventh United States Infantry to the Nacogdoches area to suppress Indian hostilities, thus freeing Houston's army to deal with the Mexican invasion.