It's pretty common to ship chicken to china for processing since the cost of shipping is lower than labor... however since it was raised in the US, it's totally legal to say "US Raised Chickens"
It’s actually extremely rare. As of 2018 there where 4 Chinese processing plants that took chickens killed and frozen in the US, thawed them out for processing, and then froze them again and shipped them back to the US. Bulk freight shipping is generally cheap, but shipping frozen goods across the Pacific Ocean twice adds up.