What would happen to Hive if all fiat-based exchanges shut down?

This post is inspired by a tweet from a popular crypto skeptic:

People act like we need to shut down the bitcoin network to stop crypto. We don't.

Almost all of the mania is retail speculators trading tokens to appreciate returns in dollars. We shut off exchange access to dollars and payment networks, the market craters overnight. Simple. 📉

Aside from the distastefulness of the sentiment in the tweet, it has me thinking, what actually would happen with Hive?

Let's imagine two scenarios. Firstly the US bans all cryptocurrency exchanges from using Dollars or making transfers to/from US bank accounts. Secondly all nation states ban crypto exchanges and transfers to exchanges with their currency (a much less plausible scenario).

How would it pan out for Hive?