For the GP's Youthstream do the transport, the guys will strip and clean the bikes and crate them up at the races, that way there is a single collection point.
The bikes are all air freighted , together, and delivered to the next race together at the same time.
I would imagine that the US bikes are sea freighted to save money, so they can send more stuff, we used to sea freight everything to WRC events apart from the cars, we had 2 40ft mobile workshops built into containers that also carried recce cars and the like, that left us in february, and didnt come back till october.
Motorsport logistics is an art form, and a constant juggle.
The only exercise i get these days, is shaking my head in disbelief