Handball would be excellent for the US, because it's fast paced, exciting, and very conducive to being a spectator. If we did have a professional handball league, I'd place it as follows among other American professional sports:
1. NFL - don't fuck with the NFL. Love it or hate it, it's king.
1A. NCAA Football - don't try to tell me it's not professional.
2. NASCAR - just be glad it's not an Olympic sport
3. NBA
4. UFC
5. MLB
6. NHL (National Handball League)
7. WWF
8. WNBA
9. MLS
10. NHL
I have every reason to believe it would take off quickly. It's got XFL-type appeal but with a legitimate athleticism and sound strategy to the game. Of course, there would probably be a few tweaks to the system for the American game - the 2 point line, for one, and probably 4 on 4 play in the final few minutes similar to NHL overtime. Other than that, why not? Violence is encouraged, the guys are huge, and it can capitalize on the fact that it's players aren't as concussion prone as the NFL.