In 2015, these were the top five most impoverished counties in the US. I'd guess these will be among the most devastated by the cuts President Trump and Elon Musk are making.

state county population poverty
1 Mississippi Jefferson 7586 48.7
2 Louisiana East Carroll 7501 48
3 South Dakota Todd 9942 46.4
4 South Dakota Corson 4149 45.6
5 South Dakota Mellette 2086 45.3