FDIC protection being invoked will still have anyone holding US dollars to rush for the doors trying to put it into anything else. There's absolutely no guarantee of protecting the value of assets, simply the number of them.
https://www.npr.org/templates/story/story.php?storyId=102384...
> But on the other hand, check these FDIC folks out. They know what they're doing. And every week they get more experience. In the 10 weeks since the FDIC took over the Bank of Clark County, 18 more banks have failed. That brings us to a grand total of 20 since the start of this year — a number that will likely grow tomorrow.
And the clearing feerate, which correlates to mempool queue depth, incoming transaction velocity, and cohort feerates, would increase dramatically.
But if there was a run to convert BTC to USD, the exchanges would not be able to cover the USD required. They'd limit or suspend withdrawals immediately. At some point someone would have to start buying with fresh USD for the exchanges to be able to pay out the sellers. With big enough news, there could be tens of thousands of dollars gap between bid and ask, which would take a long time to ease.