The lack of political will to do so. 40% of the illegal aliens in this country came here legally and overstayed their visa. Securing the border fixes only part of the problem.
And we cannot track VISA overstays? ... BALONEY... OUR GOVERNMENT JUST DOES NOT WANT TO DO IT.. Not tracking VISA overstays is a National Security problem of 9-11 proportions ... AND OUR GOVERNMENT CANNOT or WILL NOT DO IT? Absurd... totally outrageous... but it goes on and on and on...