But a much easier argument against sports betting is that it ruins the sports. Players throw. They get good at subtly cheating. The gambling apparatus latches itself to the sport, to the teams and players, the umpires and judges, the sporting organizations. With this much money on the line, it's not a matter of if but when games are thrown, cheated -- the bigger the game, the bigger the incentive. It's even easier now because of the amount of side/parlay betting that is available. It exhausts the spirit of competition.
Sports gambling is diametrically opposed to sport itself.
For example http://news.bbc.co.uk/2/hi/uk_news/426092.stm is why british people of a certain age all know the phrase "Malaysian gambling syndicates" and associate it with random blackouts.
> foreign interest in US sport is limited.
I am pretty sure that American baseball is very popular in the Carribbean and Japan. And American basketball is very popular in China due to the legacy of Yao Ming.