Your arguments remind me of "If the earth isn't flat, why don't people fall?" In other words, the problems exist only in your head.
Intelligence is what people are using to tell the difference.
It seems that you want to convince primarily yourself that there is no way in battling illegal immigration.
Hardly, and I've made that clear. Drive down Federal Street in Denver, south of Alameda. Lots of Mexicans. Can you tell which ones are illegals, which ones have green cards and which ones are citizens?