Una gran problema -  illegals send much of their earnings home to their families in MX and that money is forever removed from the US economy, instead benefitting the MX economy.  President Trump has a plan to rectify that problem along with illegal entry into our country.

Factoid:  Mexico Got More Money from USA Remittances ($25B) Than from Oil Revenues in 2015 
 
http://www.nbcnews.com/news/latino/mexico-got-more-money-remittances-oil-revenues-2015-n510346