Pershing and Patton both went pretty deep into Mexico. They were told to stop the aggression and return to the US. That is why Patton said, "What do they want me to do, give it back?" after he took Palermo.
Trump is right. We could at least manage Mexico if we owned it.
A little saber rattling, e.g., this remark, should sober up some of their leaders. They (Mexicans) are a recalcitrant species.