Even more likely, or at least less unlikely, if the petition occurs after an ATL US has admitted the Yucatán as a state.
OR, if the petition happens first, then a Yucatán admission is much more likely.
If that were to happen, then Guatemala would likely get very uncomfortable. The US is now to its north and south.
Maybe the US gets the idea of purchasing
Santo Tomas from Belgium as well.
El Salvador had a lot of overpopulation issues at the time and this tended to result in movement into neighboring countries (Honduras especially). Meanwhile part of the point of Guatemala ceding land to Britain and then Belgium was so that there could be development and settlement in the central lowlands. I can see a lot of migration from an American El Salvador into a US-administered Santo Tomas zone. That'd probably end up overflowing into Guatemala proper.
Salvadorans would probably provide the labor for the proposed Honduras Dry Canal that E.G. Squier had negotiated. Many of those workers might end up staying in Honduras. Once the canal is completed, there'd probably be a lot of movement and migration from El Salvador to the contiguous United States.
Lots of Americans in the northern triangle likes means lots of missionaries. I can see Protestantism cracking into the region sooner than it did OTL, likely being accompanied by increased literacy rates and a weakening of the Catholic Church and Conservative political power.
