O!M!G!
Just think of the jobs lost in collecting, shipping, housing, paying, pandering to, and organizing the waves of illegals coming here.
That'd be a huge economic sector (of paid panderers, supply, and logistics) thrown into disarray if we just shut the illegals out.
Not to mention all that 501C3 money flying around, and maybe not all going to the places it is supposed to...
As for economic collapse, well, I guess that depends on where you are standing in all this.