Well, being a Japanese born in Japan, I didn't have to go through a "Japanese phase", but I think I had a "foreign culture phase" in my young adult days if studying different languages and travelling to different countries count as a phase.
I had a "Mexican phase" a while ago originally because I wanted 3rd language under my belt but later got totally into its culture and language for about 4 years or so. I have been going through a "Chinese phase" for past several years because of the martial arts I study.