Article I, Section 8, Clause 18: [The Congress shall have Power . . .] To make 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.
The Soviet Union was worried that the US and China would prosper and become more powerful because of each other. Since China was so close to the Soviet Union geographically, they would rather be friends with China and her allies to protect itself and its assets.
The main reason we didn't join the League of nations is because we had the policy of isolationism isolationism = America wants to focus on ourselves, we want to stay out of trouble
