Really? Maybe that is because of passed policy just like with 9/11. You can't blame it on Bush because it increased on his watch..it was a long time coming.
And...by the way..he is the first one to historically propose closing the border..no other President has proposed that...ever.
he didn't propose closing the border only securing it and reducing illegal immigration
oh here is what Nixon did in 1969
http://www.druglibrary.org/Schaffer/library/studies/cu/CU59.html