Look at it in reverse, do games based on American shows/movies tend to sell very well?
In general, games based on American shows / movies are usually bad. There are a few exceptions. Much of the games based on anime are usually at least good or entertaining enough for a fan to enjoy it.
There are still success stories but anime generally comes after success in other media like Yokai Watch. It was very successful as a game and eventually got an anime. Similar with Pokemon.
For Anime first and then games I would say Dragonball Z has had successful games, hence they make so many of them. But even then the first Dragonball game coincided with the anime.
A good American example would be Spiderman. A popular movie franchise that finally converted to a video game.