Now obviously, we've not had a situation where an incoming executive has shut down an agency like this in terms of both personnel and financial operations.
But since (I assume) you are so clearly a rule of law guy, you obviously understand the relationship between Article I and Article II, and you certainly were a fan of this case,
https://www.supremecourt.gov/opinions/21pdf/20-1530_n758.pdf, and are obviously familiar with this case,
https://tile.loc.gov/storage-services/service/ll/usrep/usrep343/usrep343579/usrep343579.pdf, and their implications for Executive authority to undertake unilateral executive action, including in the context of foreign affairs where the President's powers are noted in the constitution.
With that background, here's a starting point for you to consider in light of these cases:
https://uscode.house.gov/view.xhtml?hl=false&edition=prelim&path=/prelim@title22/chapter32&req=granuleid:USC-prelim-title22-chapter32-subchapter1&num=0&saved=L3ByZWxpbUB0aXRsZTIyL2NoYXB0ZXIzMg==|Z3JhbnVsZWlkOlVTQy1wcmVsaW0tdGl0bGUyMi1jaGFwdGVyMzI=|||0|false|prelim. I think you'll find it interesting to see some of things that Congress actually "has" spoken about (to put it in Justice Jackson's terms), and "how" they've spoken. Some of them even surprised me, like for example 22 USC 2151-2, and in ways that don't exactly square with the last few days.
Now I'm sure that in two or three minutes you'll come back and say "I've read all of that stuff and it's irrelevant", which of course you won't have and it will just be another example of "uh-uh." So fine, you troll you. But we all know this is going to court. And to a degree, I'm fine with that, as executives test the limits of their authority all the time. But as my buddy at USAID, who is a very serious guy and whose view is that the agency absolutely had this coming and is full support of 90% of it, has told me, they will lose because they overreached. And he's right. So by all means puff up your chest - and FOR GOD'S SAKE DON'T SAY ANYTHING SUBSTANTIVE - but just don't turn into a whiney bitch when neither the district court, nor the appellate court, nor scotus, backs the administration on this. Because the dirty little secret of this Scotus over the last 4-6 years is that, while they've been striking down unilateral presidential actions you (and for that matter, often I) don't like, they've been doing so in a way that reinforces the primary of article I.