ARAWA, Papua New Guinea — On a warm morning in November, a barrel-chested and battle-scarred man arrived to Capitol Hill for a meeting he hoped would help save his struggling homeland.

Ishmael Toroama was introduced to two members of the U.S. House Select Committee on the Chinese Communist Party as the president of Bougainville, an autonomous region of Papua New Guinea in the South Pacific. But his previous occupation was evident in the arm that hung limply at his left side as he shook the lawmakers’ hands.