I would agree with the above post, in my field (academia) one does see the world boycotting the US to a degree. The example I have is that it is _much_ harder to get people to attend conformance in the US than in Asia or Europe. One conformance I attended is usually over subscribed when it is not in the US, and when it is in the US numbers are very close to the break even point. I think this is at the subliminal level more than anything else. The general consensus is that it is a lot of grief to get in to the US, it is a long way away and why bother. I don't think it is political it is just slightly too much effort.
The other point is that science is a truly international community. Therefore, to get all the top people in field together in one room means that they _all_ have to be able to get in to the US easily, not just the people from the visa waver countries.