What would you do if we said it wasn't enough time? You've booked a separate (note NOT connection) flight for a couple of hours after arrival in the US. If you miss it you will have to shell out for a new ticket unless Delta takes pity on you

If all goes well and the flight isn't late, you don't get stuck in immigration, you don't have to wait to collect luggage, US customs decides not to take an interest in you then you have a reasonable chance of making the flight