Mexico and the United States have strained border relations mainly due to the following factor:
AMexico is the largest foreign supplier of marijuana and methamphetamine to the US market
BAbundant rainfall in recent years along much of the Mexico-US border region has ameliorated periodically strained water-sharing relationships
CMexico must deal with thousands of impoverished Guatemalans and other Central Americans who cross the border looking for work
DThe US has intensified security measures to monitor and control legal and illegal transport of people and goods
AMexico is the largest foreign supplier of marijuana and methamphetamine to the US market
BAbundant rainfall in recent years along much of the Mexico-US border region has ameliorated periodically strained water-sharing relationships
CMexico must deal with thousands of impoverished Guatemalans and other Central Americans who cross the border looking for work
DThe US has intensified security measures to monitor and control legal and illegal transport of people and goods