I lived in Japan for many years teaching at an international school and I think if you want to work in the states, it's probably better to go to school in the states. If you want to work in Japan with great English skills, probably better to do your degree in Japan and coming to the states and doing Anatomy and Physiology--and other nursing pre-reqs-- at a community college along with intensive English study.
My experience as a patient in Japan has been very different than in the states. The culture of how we deal with authority figures (like doctors) is very different, for one thing. I can only imagine doing clinicals in the country you hope to practice would be a good idea. After all, many patients in the US are not exactly respectful of compliant and managing those attitudes successfully--i.e. sometimes being able to deal with confrontation-- is really important and culturally very different.
I'm a CNA now and am starting nursing school in the fall. I miss teaching in Japan but eventually it was time to come home. A point of English advice that is my number one pet peeve in healthcare: watch the intonation of "oh, really" after receiving information. If you ask it like a question, it sounds like you don't believe me.
Best of luck! Also, quick google search turned up this in terms of comparing degrees: Nursing Education in Japan