> Because it isn't part of Japanese culture to take what doesn't belong to you, but is normal for a number of Americans.

This may be hard to believe if your knowledge of American society is limited to certain strata, but it's absolutely true. If you spend some time on Reddit, on places like /r/AmITheAsshole, you'll find that a vast proportion of people outright justifies theft, shoplifting, cheating and many other sorts of unethical behavior.