It's 2022. It's trivially easy to convert investments into cash.
Of course that's assuming you're able to sell your stock and transfer the funds in a timely fashion. Maybe things have changed in 2022, but I know plenty of people (especially using Robinhood as their brokerage) who had liquidity issues when trying to sell shares in 2021.
If your emergency funds are 100% stock market instead of diversified investments you're doing it wrong.
If you don't trust electronic systems to stay on-line in a crash then your hedge is probably not USD but other assets, like canned goods / water filter / ammo / hard assets in your personal custody.