I'd ballpark USAID at maybe half a percent? It's an easy win. A few more of these and Elon will have made a meaningful dent in the wastage of my tax dollars.
I'd consider even a 3% reduction in spend a massive success. The percentage of money being wasted is much higher, somewhere between 30% and 70% (estimates vary.)
If you've ever worked for a government contractor you've seen the immense waste/scam firsthand.