Poorer countries and generally countries with worse governance have a real trouble controlling tuberculosis. Given how much of it is asymptomatic, you have to have a real screening program including X-rays in order to catch cases, and that is beyond the ability of most developing countries - which are precisely the countries where most of the population boom is taking place.

I don't believe that USAID can cover, say, the whole of Africa with preventative care. The US cannot cover even all of its own citizens, for a host of reasons, much less 1,5 billion people in exotic regions far from its borders.

Purge of USAID is likely to make the situation worse, but only marginally worse. The real problem is that at least third of humanity doesn't yet have any reasonable healthcare infrastructure, reliable grid (for medical machines to work), public safety (for doctors to survive), etc., etc., etc. If we had a functional recipe to solve such problems, they would likely be solved already.