They can defund the whole office, subdivision, or function.
Life isn’t an episode of the apprentice… nobody in congress sees their oversight role as firing random post office clerks. That’s idiocy. Congress controls the law and the purse. Conservatives have been wielding this power for years - that’s why single moms are routinely nabbed in audits for earned income fraud, while rich people get away with donating millions to phoney foundations that they control for years. (Congress limits funding for enforcement)
The executive has broad authority to take personnel actions while adhering to the law.
