Actually the weirdest thing was my old karate sensei when I was a kid spoke grammatically inferior english to the Japanese shihan who was her teacher. She spent quite of bit of time living in Japan and Okinawa as a deshi. Werid, considerly she was a farm girl from Iowa. Shihan, had a fair accented english, besides being in school for english ( the sensei herself was a college graduate ).
My dad ( who became fluent in Nihongo through college and living o'er there ) would sit and watch class and always laugh at why she was far more difficult to figure out what she was trying to say than shihan.
We were actually talking about this happening when Japanese come to America and vice versa with my friend's roomates who are all from Japan.
My english back in those days under those two sensei suffered a bit in speaking. Eventually, after getting coaching I have become quite the straight to the point American style speaker...errr.