Destroyed by Trump. According to the rating agency, they'd lost confidence in the ability of the US to repay debt for several reasons:
1) Growing debt levels caused by Republican tax cuts (a little basic accounting: If you don't generate revenue, you have no money to spend)
2) The constant brinksmanship and bickering over raising debt levels which has little to do with sound fiscal policy and everything to do with political posturing.
3) The Jan 6 fiasco - When the president of a nation attempts to overthrow the democratic process in a political coup (no matter how poorly executed), it doesn't fill creditors with faith that their own agreements will be honored by said government.
All of this can be laid at the feet of the dysfunctional Republican party. This is what all of your squabbling and irresponsible game-playing gets you.
https://www.nytimes.com/2023/08/01/business/fitch-downgrade-us-credit-rating.html