You've got to look at the big picture

Sure in the short term that might be easier, but in doing so you sell yourself out

Everyone knows Trump's reign will be short.  If I'm Mexico, I'd seriously consider just riding out his term and then regrouping with the next president.  Realize especially if Trump alienates other nations too (apparently Germany is well on its way), the world is not going to side with Trump on this - they will side with folks like Mexico.  

Mexico CAN win this if they play it right.  But only if they stand up for themselves.