Offhand, I'd say Mexico's doing pretty well. It could certainly do better.
If you could have butterflied the Maximato, where the PRI indulged in a rather pointless spate of autarky and pretending the neighbor to the north didn't exist from 1930-1980 they'd have had even better economic growth.
The tough problem you've got is that the USA served as a safety valve. The people really pissed off about PRI corruption and conditions in Mexico could come to the USA, instead of agitating for change within Mexico.
It wasn't easy for the emigres in the USA and their leaving (and sending money home) made it easier for the PRI to run their own shop in a steady state as if things hadn't changed for seventy years.
A BIG POD would be USA not deciding in the 1970's to internationalize the internal fight against marijuana, then cocaine, heroin, and meth.
The PRI seized on it as an excuse to screw with poor Indian farmers, defoliating and burning crops, which exacerbated a lot of already-extant social tensions between offical Mexican culture and various indiginous communities.
I'm shocked more indigenous activists haven't gone the Colombian route of
using drugs to finance revolutionary movements.
It'd remove the three-corner war fought on Mexican soil between the DEA, federales, and the various cartels that kills so many people.
