Please tell me you weren't in INDY!!!!It does work.
It gives you a few seconds to kick them in the groin while they try to understand what you said.
But sometimes it can also be a problem if they notice that you are not from the area, talk with an accent and such.
They also think that you carry lots of cash since you are a tourist and think that you dont have any weapon on you since they believe you just walked out of the airport.
The last guy who tried to mug me in the US had the bad surprise of learning that I had no cash but a few weapons.
the rest I find very true.