this is something quite different. Congress determines funding, but it has never gotten into specific allocation within the USAID budget - that has been done by an unelected bureaucrat.
Allocation of the funds generally approved by congress has been decided an unelected bureaucrat within USAID (who has shown a pattern of corruption and strong preference to the Democrat Party). Certainly the POTUS is far more worthy as the highest elected official in the land to choose allocation rather than an unelected bureaucrat!.
Trump has every right (and in fact a legal obligation explicitly described in his oath of office) to prevent harm to the American people - this includes misuse of tax payer money. Yet, even so, it isn't Trump himself who will be re-allocating the funds for now,,,,,,,,,
Trump's Secretary of State Marco Rubio - head of the State Dept (under which USAID resides)- approved by congress has placed himself as director of USAID. He will re allocate the money into the tax payer account by not spending it until congress can vote to defund them completely in a month. In the meantime, Rubio has promised to continue legitimately useful funding in the meantime (such as legit medical aid). Should you somehow flip a few R's, it won't matter - congress can vote to fund the money, but the head of USAID can allocate at his discretion as has always been the case - including back to the taxpayers.
By the time you work your way through the courts, congress will have already decided the issue and the case will be dropped by the courts. If you make that far since you will be arguing to a court that the POTUS does not have the right via his State Dept head approved by congress who has overall responsibility of USAID to prevent the American people from having their money wasted.
Boom.
Many edits d/t poor typing - done now.