Opinion polls indicate that most Americans want to tighten immigration rules. It's little wonder, given recent headlines shouting about boatloads of smuggled Chinese aliens, terrorists who tried to blow up the World Trade Center and economic troubles in cities crowded with immigrants. Many of the solutions being proposed focus on illegal immigrants. Responding to the public outcry, President Clinton has asked Congress for legislation to stop fraudulent asylum claims and provide more Border Patrol agents. But more and more critics want fundamental changes to the system that governs legal immigration. Citing the growing economic, environmental and social burdens that they say immigrants impose on U.S. society, they call for a major reconsideration of the United States' traditional role as an immigrant nation.