Can you give me some reasons why Hockey is not as popular in the United States as many other sports?

Yes,

1. Hockey requires a field of ice which can only naturally occur in colder climates which limits the geographic appeal of the sport. Also, ice rinks are not as readily available around the country as, say, a soccer field or basketball court.

2. Hockey is an expensive sport to play. One needs to purchase pads, sticks, helmets, and other gear, as well as rent out an ice rink for practices and games.

3. In addition to cost, the barrier for entry related to skill is quite high compared to most other sports. One must first be able to ice skate before playing hockey which is a skill many people don't have.