(After JET) Should I Pursue a Masters in Japan before a Phd in the US?

I posted this in GradAdmissions too but thought the collective wisdom of the JET sub might be more helpful.

I'm an American with an undergrad degree from a US university. I'm currently working on the JET Program. My intermediate goal is to pursue a Phd in Japanese Studies (or Literature) in the US, and eventually try to get a job in academia. I'm considering applying for a masters degree at a Japanese university. My thought is that this will give me a second opportunity in the country beyond the JET Program, help perfect my language skills and allow me to experience a different academic culture. But I'm also assuming/hoping that the masters will enhance my application to a US graduate program and give me some transferrable credits at a lower price than they would be in the US. Do these assumptions hold any water? Will a US Phd program in Japanese Studies be impressed with a Japanese masters? Will the credits transfer? If the program is really just an extended holiday, it may not make sense. Thanks for any advice.