I'm not sure if this alone would be enough to guarantee the long-term survival of the Empire, but it would be a very interesting scenario if it did! Being an empire on a continent of republics, I suspect Mexico might not have the warmest of relationsh with its neighbours, and it would quite possibly seek close relations with either the UK or France. It would be interesting to see if the european revolutoins of 1848 would have ripple effects in this empire. Republican ideas would likely be a fairly common issue the emperor would have to face. I speculate it 19th century Mexican history ITTL may look somewhat like 19th century Spanish history OTL; that is to say, chaotic. Lots of swinging between more absolutist governments, and more liberal governments, with rebellions and revolutions of the opposite tendency whenever one is in power.
en.m.wikipedia.org
