Having just spent some weeks in Europe as well as all over the Lands of the Bible, one thing that was noticeably and mercifully absent was bumper stickers.  I saw almost none on the thousands of cars I saw.  Americans on the other hand wear their hearts on their bumpers, not their sleeves.  And sometimes its way over the top.  For example,

Never mind the fact that if a driver actually tries to read all or some of these stickers they themselves may run into the car that is bestickered, but frankly some bumper stickers just shouldn’t see the light of day.