Someone always fills the void, in this case it would likely be China. USAID only gets $50 billion, that's hardly enough to control the world on the scale that I think you're saying is happening.
Against a top-20 economy, sure. $50 billion doesn't look that big to somewhere like Korea with a GDP of around $2 trillion. But against the ones outside the top 30 it is a lot of money. Malaysia @ 34 [0] only has a GDP of less than $500 billion and they're a pretty big country economically speaking.
An annual budget of 50 billion and a defeat-in-detail strategy can get a lot done over the years. Picking a random country like Ukraine, their peak GDP never reached $200 billion. And there is a suspicion [1] that 80-90% of their journalists are being funded by foreign grants with involvement from USAID. It isn't entirely fair to compare the entire USAID budget to Ukraine's GDP, but the point stands that if USAID wanted to reshape Ukraine they have the resources to do it.
