This is true, sort of the bandwagon effect. It has something to do with "going with the flow", not upsetting the applecart etc.
Prior to 9/11 the flow was in the direction of more amnesties and benefits for the illegals. But since then, it seems, at least for now, to be going in the other direction of tightening things up. And you're seeing more politicians talking that talk. It's a lot more difficult now to label someone a "racist" for wanting to close the borders to keep out potential terrorists.
The idea of just doing away with borders and letting in anyone who wants to come here is not conducive to national security or cohesion. Hopefully the events of 9/11 will have opened some of the eyes of those like Ben Wattenburg. But Bob Bartley is a lost cause. He's just quieted down for now, but he'll be back when he thinks it's ok to start his nonsense again.
I agree that there has been a attitudinal change even among some of the One Worlders since 9/11 but I would hope that it is not just the terrorist threat that is driving a slightly less reckless approach to immigration in DC these days. We, as you know, are continuing to pile in immigrants from 3rd world countries from around the world at a near parabolic rate and if history is any guide this will cause serious problems in the years to come.