That is so true......it’s a 70 year old problem, give or take, and it’s all caused by poor government policies (on both sides of the border) - a failure by our government to even carry out the good policies, time, opportunity and human nature.
When you add opportunity plus human nature....like say the opportunity to sneak across and let gringo government support you - then human nature dictates that many are going to do that.
The other dynamic in this is that approximately 40% of Mexico’s GDP is derived from the money illegals send back home every month from the US. Cut that off and Mexico collapses completely. If you really wanted to punish Mexico all you have to do is shut down the Western Union telegraph service from the US to Mexico.