I can understand your feelings on this matter; as they are similar to Jonah's.
He just KNEW that Ninevah was going to be destroyed.
Jonah 4:5
Jonah had gone out and sat down at a place east of the city. There he made himself a shelter, sat in its shade and waited to see what would happen to the city.
Jonah was angry at the Lord for sparing Ninevah, because he told them they were done for and when God relented, Jonah felt his "reputation" was ruined.
I would rejoice if God relented upon His anger and judgement at America.
However, we should also reflect that after Ninevah repented, they went right back to their old ways, and God wiped them out.