Sen. Bill Nelson, D-Fla., a member of the Senate Armed Services Committee, welcomed the charges against Snowden.
"I've always thought this was a treasonous act," he said in a statement. "I hope Hong Kong's government will take him into custody and extradite him to the U.S."
But the Government Accountability Project, a whistle-blower advocacy group, said Snowden should be shielded from prosecution by whistle-blower protection laws.
"He disclosed information about a secret program that he reasonably believed to be illegal, and his actions alone brought about the long-overdue national debate about the proper balance between privacy and civil liberties, on the one hand, and national security on the other," the group said in a statement.
Michael di Pretoro, a retired 30-year veteran with the FBI who served from 1990 to 1994 as the legal liaison officer at the American consulate in Hong Kong, said "relations between U.S. and Hong Kong law enforcement personnel are historically quite good."
"In my time, I felt the degree of cooperation was outstanding to the extent that I almost felt I was in an FBI field office," di Pretoro said.
The U.S. and Hong Kong have a standing agreement on the surrender of fugitives. However, Snowden's appeal rights could drag out any extradition proceeding.
The success or failure of any extradition proceeding depends on what the suspect is charged with under U.S. law and how it corresponds to Hong Kong law under the treaty. In order for Hong Kong officials to honor the extradition request, they have to have some applicable statute under their law that corresponds with a violation of U.S. law.
Disclosure of the criminal complaint came as President Barack Obama held his first meeting with a privacy and civil liberties board and as his intelligence chief sought ways to help Americans understand more about sweeping government surveillance efforts exposed by Snowden.