The main difference between an American and European Roulette wheel is the number of green pockets / zeroes. The European roulette wheel features one green pocket (0) whereas the American Roulette wheel (more popular in Las Vegas) features two of them: 0, 00.
The European roulette wheel is comprised of 37 pockets, numbered from 0 to 36, whereas, the American roulette wheel has 38 pockets, with the additional pocket being labelled as double zero (00). The additional pocket on the American roulette wheel can make all the difference when it comes to winning odds.