USAID still exists on paper. But under the current appropriations bills, the funding is allocated to the State Department.
https://www.congress.gov/bill/119th-congress/house-bill/4779...
Moreover, the impoundment rules don’t require congress to act first before the president acts. They require the money to be spent, but if the budgetary authority is provided over a year it’s hard to say when the president must spend that money within the year. (Unless there’s specific requirements in the statute.)
It's absurd to argue the executive can intentionally delay and shuffle money earmarked specifically for certain purposes, like USAID. Why not just give the executive all power over the Treasury? Why have Congress at all?
There was a few months of overhang, but the Supreme Court ruled that the administration had to pay out billions of dollars that were already allocated to contracts during that period.