Why did the us congress oppose the signing of the treaty of Versailles

it did not want the U. S. to be involved in international politics.

They didn't want the U. S. involved in foreign affairs

Explanation:

Congress was worried that, because of a treaty, the United States of America could be obligated to get involved in some foreign war. They did not want that obligation on their shoulders since they didn't want the country directly involved with overseas conflicts.