"Over 68 million Americans leave the safety of our borders every year. If danger strikes, the FBI's International Response Team (IRT) is called into action."
The International Response Team (IRT) was a subdivision of the FBI. Led by Jack Garrett, their main task was to solve international crimes and rescues US citizens who find themselves endangered while abroad.
The mission of the IRT is nearly similar to the BAU, but in this case, they travel across the globe to aid the foreign law enforcement to solve international crimes and rescuing Americans and bring the victim home safely.