For context: Tuberculosis treatment requires strict, months-long medication adherence. Even a brief disruption means patients may not complete their courses, allowing drug-resistant TB to emerge. These strains are far harder and more expensive to treat, spreading across borders and undoing decades of progress.
The brief (?) interruption to PEPFAR (Bush's HIV/AIDS aid program) has major impacts too. One of the plainest ones is that infants with HIV can, if anti-retrovirals are paused, die more or less right away.
- "In children who acquired H.I.V. at birth, the infection can progress very quickly to illness, with death occurring as early as eight to 12 weeks after birth — shorter than the 90-day pause on foreign aid."
It also makes the point that, under some reasonable assumptions, you could assume that any domestic program you could theoretically redirect the funding to would likely be ~100x less effective than PEPFAR, which is an abnormally effective aid program.
Reasonable assumptions would not assume you to assuming the US' top medical bureaucrat being a conspiracy theorist who denies the existence of HIV (and asserts AIDS is environmental and that anti-retroviral drugs are dangerous toxins).