US banking and credit union groups are voicing concerns over cryptocurrency firms seeking bank charters, citing "serious policy and procedural concerns." A letter sent to the Office of the Comptroller of the Currency (OCC) highlights worries that granting licenses to stablecoin issuers like Circle and Ripple Labs could create legal and policy problems. The groups are requesting transparency, urging the OCC to make these applications public for scrutiny. Ripple Labs, Circle, and BitGo have previously sought authorization to establish National Trust Banks, aiming to offer banking services within the cryptocurrency sector. Traditional banking institutions are wary of the potential risks and regulatory complexities involved in integrating cryptocurrency businesses into the established financial system. The outcome of these applications could significantly impact the future of cryptocurrency regulation and its integration with traditional finance in the United States. ```