What should I do with my US bank and brokerage accounts if my visa isn't renewed?

Act before you leave, while you still have a U.S. address and online access. You generally can keep a U.S. bank account and brokerage account after departing, but you must update the firm with your foreign address and tax status (file Form W-8BEN), which may change withholding and, occasionally, prompt a firm to restrict the account. Don't abruptly close everything, an open account makes it far easier to receive a final paycheck, tax refund, or 401(k) rollover. For retirement accounts, decide whether to leave them, roll to an IRA, or take a (taxable) distribution. Set up a trusted contact and keep your login, beneficiaries, and phone number current. Plan the wind-down deliberately rather than in the final week.