Could the US Government Self-Host a Fediverse Server?

In response to Joe Biden and the White House enabling ActivityPub federation via Threads, a number of people asked: "Why didn't the White House just self-host their own Mastodon server?"

Here's some very basic musings on what it would take for that to happen. and what some of the hurdles are. Don't consider it a definitive answer, but a jumping-off point.