HONG KONG—The U.S.'s crackdown on global tax evaders is prompting some Americans in Asia to rethink their citizenship, attorneys there say, in part amid an increasing burden of paperwork required by U.S. tax law.

"When I became an immigration lawyer 30 years ago, people really were excited about going to America. Now, more than half of my clients are people thinking of other alternatives rather than people seeking to immigrate to America," said Eugene Chow, the principal of Chow King & Associates in Hong Kong....