The Durbin Amendment required 2 unaffiliated networks be present on US debit cards. So a Visa branded debit card for signature purchases would need a network like NYCE for pin purchases. So US banks who had been intending to implement the same EMV standard used in the rest of the world had to create a new standard for their debit cards, new software for chip terminals a whole new routing protocol for the payment networks. Very expensive and delayed the implementation of chip cards in the US by 3 years. However it doesn’t prevent pay at the table.