Mexico is a narco state involved in what is virtually a light civil war. Governments which switch back and forth have one cartel or another behind them and there is a huge disconnect between the President and Military.
They would be lucky to be a vassal state, but they need to play ball first. We are not an open border dumping ground for them to ignore their problems, nor are we a black market source to provide their criminal organizations with funding.
I see them getting paid to secure their own Southern Wall, but unless they shed their culture of corruption things will be icy.