Is TSA rescreening required when transiting internationally through Orlando airport?

Orlando is a bit of an oddity in the respect to international arrivals due to the way luggage is (or at least, can be) handled.

Presuming you are not arriving from a Pre-clearance airport, then yes, you will need to re-clear security as well as immigration and customs in Orlando.

The flow in Orlando will depend on whether you have bags, and whether you are able to check your bags to your destination or not.

Upon arrival, you will go through immigration, collect your bags (if you have checked any), and then go through customs. If you have bags, and they have been checked through to Miami, then you can then re-drop your bags at the baggage drop, hop onto the train to the main terminal where you will re-clear security at the general TSA area, and head to your gate.

If your bags were not checked to your final destination then there's a few options. If you have at most one bag, then you can take the bag with you on the train, and re-check it with your new airline at the main terminal.

Alternatively - and there is where Orlando is different to most airports - you can drop your bag at the baggage re-check area and it will be transported to the baggage carousel in the main terminal for you. You then catch the train to the main terminal, go to the baggage claim area, and re-claim your bag before checking it in with your next airline. Doing this will take longer than taking your bag with you on the train, but it may be easier, and is mandatory if you have more than one (large) bag.

You can find a brochure that covers some of the details for this process on the MCO website, but keep in mind that this is really designed for arriving passengers, not connecting passengers.

United States airports are not built to handle international transit passengers. Transit doesn't exist. Maybe once did but 9/11 and consequent things put to an end of it perhaps 2003 or so.

This means once you've landed you will be funnelled through immigration then you will need to collect your bags then go through customs and then you will find yourself outside of the secure area.

Edit: yes, if you are coming from a preclearance airport then this is different but for immigration purposes you are already on a domestic flight in that case! This will show in the terminal you land etc.

The US doesn't have international transit, which means everyone not pre-cleared at the airport of departure (in Dublin, Shannon, Abu Dhabi or most Canadian airports) must get out of the sterile zone into the public area (after clearing immigration and customs) and then re-clear security.

While some airports, such as Washington Dulles, have dedicated immigration, customs and security areas for transit passengers, Orlando does not. As such, you will go through the same security check as those beginning their journey in Orlando, unless arriving from any of the above mentioned airports, in which case you'll find yourself in the departures area and can immediately proceed to your next gate.