The U.S. should be way more concerned about Mexico. We share a very long border with our neighbor to the south. What happens in Mexico can really come back to haunt us. They have a huge drug cartel problem which brings drugs and violence back over into our communities. Their economic situation also results in a lot of illegal immigration here in the U.S.
Considering that we share a border that's thousands of miles long with them and are in a free trade agreement with them, I would say that it's a pretty fair idea that we need to be concerned about them.
If nothing else, we need to be concerned about the drug cartel violence that is going on down there spilling over into our borders.
The U.S should be more concerned about Mexico for a number of reasons. For one the immigration between the border of Mexico and U.S should be more secured. Also the drugs and the numerous of criminal acts which are occurring between the border should be a big concern from the U.S
The U.S. has at certain points in history had contentious relations with Mexico. Even now, the Mexican drug cartels have spoiled the relation between the two nations.
Having a strong relationship with Mexico is very important due to immigration. It is also important to maintain key avenues to resources in the region.