The reason for adding a bank card to a US account is that in the United States, most online shopping, payment and subscription services need to be paid by credit card or debit card. Therefore, when creating a US account, the system requires users to add bank card information to complete account registration. In order to ensure the payment safety of users, the relevant laws and regulations in the United States have certain provisions on online payment, including the requirements for payment methods, such as security measures for credit cards and debit cards, and restrictions on use. Therefore, in order to comply with relevant laws and regulations, online payment service providers in the United States often require users to add payment methods such as bank cards, and require users to provide relevant authentication and security measures to ensure the safety and legality of payment.