Only individuals can repent of their own individual wrongs. If a large number do it altogether, it’s still individuals.
But they can do it as a nation. Not that I think The U.S. will. It is too far gone. I expect God's judgement on it, else He will owe Sodom and Gomorrah an apology.
but God judges nations and nations can repent.
Jonah 3: 5Then the people of Nineveh believed in God; and they called a fast and put on sackcloth, from the greatest to the least of them. 6 When the word reached the king of Nineveh, he got up from his throne, removed his robe from himself, covered himself with sackcloth, and sat on the [b]dust. 7 And he issued a proclamation, and it said, “In Nineveh by the decree of the king and his nobles: No person, animal, herd, or flock is to taste anything. They are not to eat, or drink water. 8 But every person and animal must be covered with sackcloth; and people are to call on God vehemently, and they are to turn, each one from his evil way, and from the violence which is in their hands. 9 Who knows, God may turn and relent, and turn from His burning anger so that we will not perish.”
10 When God saw their deeds, that they turned from their evil way, then God relented of the disaster which He had declared He would [c]bring on them. So He did not do it.