What trading country in the Pacific was the most important destination for the United States in the early 1900s?

China

Explanation:

The appeal of profits to be earned from the China trade served as the initial impetus to motivate U.S. citizens and officials to enter into the Pacific region.

necessary and proper clause. the congress shall have power to all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution in the government of the united states, or in any department or officer thereof.