The Japanese are a truly pragmatic people. Exercise is important, sure. But why not use that time to also learn some valuable phrases in English? I mean really, when you get to America and you find yourself alone in a dark alley with some really scary dudes, what use is it to know how to say, "My hotel is located at...". No, clearly that would be useless.
If handing over all of your valuables doesn't work, this will probably come in handy.
And after you you've completed your meeting in the alley, you surely don't want any confusion when you find a friendly local Policeman. Do you?
And visiting America is not all about confronting dangerous individuals. If you're not used to our water, there's a little thing called Ben Franklin's Revenge.