If you checked a bag, you'll have to collect it from baggage claim from the international flight. You'll need to clear customs and immigration. Next, you'll recheck your luggage for the domestic flight.

Yes, in the vast majority of cases, if you are arriving in the U.S. on an international flight and connecting to another destination (either domestic or international), you must pick up your luggage at your first port of entry. This is because you must clear U.S. Customs and Border Protection (CBP) with all your belongings. After you pass through immigration, you head to the baggage claim carousels to retrieve your bags. Once you have walked through the Customs exit, there is usually a dedicated "Baggage Re-check" counter immediately outside where you can place your bags back on a belt if they are already tagged to your final destination. You do not need to go back to the main check-in desk. The only major exception to this rule is if you are flying from a "Pre-clearance" airport (such as those in Canada, Ireland, or the Bahamas), where you clear U.S. customs before you even board your flight, allowing your bags to be checked through to your final U.S. destination without interruption.