For me, Japanese gestures, such as bowing, are intimately connected with the language, so when I'm speaking Japanese, even in the States, the bowing reflex gets activated.

The one gesture I sometimes find myself making is the "chop-chop" gesture that people use when moving through a crowd or crossing a street.

After I returned from actually living in Japan, I had two residual effects:

1) I kept expecting my shoes to be at the front door. I would get up in the morning, do all the usual morning things barefoot, and then realize, when I was ready to leave the house, that my shoes were still in the bedroom.

2) For a while after coming back, whenever I approached a sales counter or asked someone for directions, I had to stop myself from saying, "Sumimasen ga..." because that was the first thing that came into my head.