Withdraw from Middle East conflicts. Send troops into Mexico

It doesn't make sense that we spend so many resources fighting in countries halfway around the world, only to have them go back to their former ways.
If we are so willing to help a country, who's people are being oppressed, why not use those military resources to assist in clearing out the drug cartels plaguing the people of Mexico.
1. The drug cartels spread their drugs and violent throughout the United States, especially in border states.
2. It would alleviate much of the illegal immigration problem. The crime and corruption caused by the drug cartels is are big reasons why many Mexicans cross the border. If we take away the drug cartels, illegal immigration wouldn't be such a problem.
This wouldn't trample any treaty regarding military action against Mexico. This is just helping them