I have to disagree with this.
I mean, is immigrating people dangerous to the USA and natural born U.S. citizens? Sure.. its very dangerous. However, I don't think that the U.S. government would let it get to that point to begin with.
They would put a halt on ALL immigration... and sure, you would still have people such as the dirty Mexicans from Mexico trying to get across the U.S./Mexico border into the U.S. for a better "life". Border Patrol agents know what to look for, as far as being able to tell the difference between an innocent person/family (whos really truly looking for a better life for his family) and a group/single individual that is simply wanting to come across in order to drop off/deliver his/her/their drugs for money.
IMO, they need to close the U.S.A/Mexico border COMPLETELY.. and for GOOD. If they would make it big enough.. and long enough.. it would work. But currently, there are too many gaps in the border wall.. and thats a big problem.
But again, if immigration started to get out of hand.. the U.S. government would shut it down.. all immigration would be declined.. and border patrol agents would be on high alert.. and probably be given the authority to use deadly force (which they already do.. I'm talking on a higher level). The borders are monitored 24/7 all year round.. not only by physical beings (patrol agents) but also by remote monitored cameras that are mounted at various points along the border wall structure.
Sooo.. yeah, I don't see it ever getting to a critical point. If it ever does, well.. like I just explained...
peace.