Upvote:17
Contrary to most other countries, there is no sterile international transit in the US.
All passengers arriving in the US, whether it's their final destination or they transfer to a domestic or international flight, will have to:
After customs, if you are on a single ticket and checked through to your final destination, you will be able to drop off your bags (already tagged for your final destination) at a counter just after exiting customs. You can then go to departures, through security, and to your gate (possibly changing terminals in the meantime).
If you are on separate tickets, you will have to go the the check-in area for your flight to check-in and drop your luggage before you can go through security and to your gate.
There are two exceptions:
Note that in all cases, since you will be entering the US, you need to meet all requirements for entry into the US, not only from an immigration point of view (as described above, US passport, green card, visa or ESTA), but also for Covid-related measures (vaccination and recent test).