Rita -- I'm only able to give you my own subjective opinion, not hard facts. I'm pretty oblivious so I probably just didn't notice it in other places...but I saw a TON of bumper stickers in northern California. Also Oregon. Those are two I can think of offhand.

I'm not a world traveler, but you are Jodi -- well, at least a good part of the USA. Tell me, what states or regions have the most bumper stickers? I was recently in Minnesota, and saw a lot of clean cars -- no stickers, not even a "support the troops".