That sounds weird. I can understand that you cannot take money that was promised for thing X and spend in thing Y but if you can reduce the X spending I don't think there is any issue.

Now I do not know if Congress has explicitly required X to provide certain thing. If they did then there might be some issue if X fails to provide it. It's probably easy to say someone is accountable for it if it's something objective (let's say building for Congress) but if it's subjective it could get tricky.

No, the executive is not allowed either to redirect or to stop or slow the Congressionally apportioned funds.

This is called impoundment and it's unequivocally illegal.

No wonder everyone always tries to figure out how to spend money if they still have some left before end of the fiscal year. Some individual "I saved us $1 million by shutting down servers we don't use!" Manager "Fuck, now need to quickly figure out some way to spend $1 million..."

That's a much more mundane bureaucratic imperative that exists at every level in every budgeted system. But yeah, that more mundane imperative definitely doesn't help to control costs in the next budget cycle, for sure.

Most of the US Government spending is on things that are fairly fixed and fairly known. There isn't a lot of elastic spending like this, or at least not in a way that really turns a dial.

Correct. But Congress doesn't and didn't ever say "spend $250k on transgender operas." Congress' laws are ambiguous and rely on the administrative state to dish out money to a specific cause. The law probably said something like "promote health policy in the Europe".

The Trump administration will repurpose those funds to things more aligned with GOP preferences.