Until two years ago, Americans were secure in the knowledge that, at least at home, they were safe from international terrorists. Then Islamic fundamentalists sent a shocking wake-up call - the bombing of the World Trade Center in New York. In April, Americans were shaken again when a powerful blast destroyed the federal building in Oklahoma City. But that attack - the worst case of domestic terrorism in U.S. history - apparently was perpetrated by American citizens. In response to the escalating terrorism against the U.S., the Clinton administration and the Republican-dominated Congress have presented several anti-terrorism proposals. But some observers question whether they will work, whether they are constitutional and if future terrorists will up the ante, using even more deadly techniques.