1.What is the most popular breed in America?
The answer you are looking for is the Labrador Retriever. According to American Kennel Club registration statistics (for year 2000) there was at least double the amount of Labs than the second one on the list, Golden Retrievers. But, truly the most popular dog in America is the mixed breed, mutt, whatever you want to call it.

2.Which breed has bitin the most people in the year 2000?
I know last year some organization (don't remember which) came out with Rottweilers as the top biters.

But, you have to take into affect all the bites that are not listed with officials. Which might rack up some more points for the small dogs, because when they bite, it doesn't hurt as much as when big dogs bite.

Also, if you're going to count every bite, does that include when a police dog bites?