This is a hypothetical question because the following may or may not happen.
HYSA is considered a safe for emergency funds because they are insured by FDIC up to $250K. Another safe emergency fund allocation is T-bill and associated ETFs and MMFs like SGOV and VSUXX.
If FDIC is repelled then no HYSA is safe because there is no insurance once the funds are misused. And if the current administration decides to not pay interest on T-Bills then there is no point investing in T-bills. To add to this the story coming out of NY that 80 million of federally allocated FEMA funds were taken back shows that the federal government can pick a chose who they want to give money to and who they want to take money from.
Keeping just cash is useless because it erodes away due to inflation.
where do you invest your emergency funds? The show that follows the above situation is a whole different story.