I believe that we do have already the infrastructure in place to monitor and control the influx of travelers and visa applicants. In a global environment, we also have to think about the percussions. The visa application process is, as far as I know, somewhat a "tit for tat" system. If we tighten the borders, all other affected countries will respond, have to respond accordingly and business as well as leisure travel will become more difficult. While this may be a small sacrifice for a perceived gain in security it is another step towards an isolated, unfree, uninviting America.