whats the best way to tell if a newer pk is us made?

A US built PK will have the serial number on the right rear dropout starting with PK and a Fuji built PK will have a long serial number on the bottom bracket shell. The American and Fuji PK's are physically very different so they are easy to tell apart. Another easy sign is that an American PK uses a 7/8" seat post (after 84) and the new Fuji stuff is bigger than that. Also any American PK from 85 on has an integrated (built in) seat post clamp and the new Fuji (03 and on) uses a standard seat clamp.

thanks for the info.