Since the Unlawful Internet Gambling Enforcement Act of 2006 which is an act which was formed part of the port security bill there has been many US facing sportsbooks taking the step of moving away from US based domains such as domains with the .com extension. As an Internet based company they rely solely on customers coming to them through the Internet and by these domains being seized by the US government makes it difficult for them to conduct the day to day business.
The US has placed pressure on banking institutions to block gambling related transactions. However the majority of gambling operations have licenses in other countries which clearly allow their licence holders to cater for players from around the globe and this includes players from the United States.
In 2011 the US were able to successfully seize several gaming operators websites causing some of them to collapse. This was based purely on indictments made against the gaming operators on how the money came into the company and was treated as a criminal case and operation.
We have researched the web on the top gambling operators who catered for the US market in the past who also continue to cater to the US to see what domain extensions they are now using. In no particular order here are our findings;
Bovada.lv (originally bodog before the management sold to Bovada)
There are some sportsbooks such as wagerweb.com who continue using the .com domain extension. Worth noting those who are licenced in Antigua have gone for the .ag tld.