Not from the US, but for example anti-lockdown campaigners in Canada had their bank accounts frozen IIRC
For reference as I hadn't heard about it before:
> Isabelle Jacques, assistant deputy minister of finance, told a committee of MPs that up to 210 bank accounts holding about $7.8 million were frozen under the financial measures contained in the Emergencies Act. - https://www.cbc.ca/news/politics/emergency-bank-measures-fin...