I’ve had some minor experience with an org that’s just barely big enough to have a bank account. Getting all the paperwork together to set it up is such a pain in the ass, and then when you elect a new treasurer it’s almost like starting the whole process over again. We used the Bank of Labor for a bit, thinking they would be sympathetic and not a total pain in the ass, but it was a worse experience than just using a local credit union.
A big part is that the American legal system is set up to only support bourgeois institutions, and makes it difficult to have a democratic organization.
EDIT: to actually answer, if you’re looking to set up a bank account, you should start by going to a local credit union and asking them what information they need to set one up, so that you can then structure an organization to meet the legal requirements