Alot of stuff happened in '65, so finding cause & effect might not be that simple.
I think something modeled on the old Bracero program is appropriate. But from what I've heard of it, what GW is proposing far exceeds that.
The big issue is that the Mexicans, by and large, came up for the season, by themselves, and headed back down to Mexico in the off-season.
After the guest worker program ended, each border crossing became a hazard. To minimize the level of risk, the now-illegal aliens crossed ONCE and stayed here. They also started bringing their families with them.