When the treaty of Versailles was negotiated (without the Germans mind you) they didn’t refuse to allow German delegation. They didn’t invite the Germans because they were under the impression that the Germans had surrendered (instead of the cease war that meant neither side won.) Since Germany had “lost,” the loser had no say in the terms of the treaty and was forced to accept it.
The treaty of Versailles was one of the causes of World War II.
President Truman, along with many prominent politicians at the time, believed the United States should sign the treaty because he thought it would prevent another World War II, but most importantly the spread of communism.
Common sense was what shifted the grievances.
The federal government was too weak, and couldn't enforce their laws. They had borrowed money for the Revolutionary War and couldn't pay their debt. They also lacked the power to tax.
Therefore, the answer would be the first one.
