First would be to round up the ones with a criminal background. The rest would be harder. Not only are illegals from Latin America but almost half are from Asia, Russia, China, India, the middle east, Europe, Africa, and even Canada. You would have to issue some form of new government ID, one that would be difficult to forge to assure that you were born in the United States. Next would be the formation of a special immigration “police force” that would have powers of arrest and detainment. Everyone would have to submit to searches and stops and raids. Rounding up illegals will take years.
All immigrants have green cards and are required to carry them.
In states that comply with SAFE Act, drivers licenses are secure proof that they either produced a green card or a birth certificate.
It’s easier than you think.