Found this online
Below is from 2 years ago, they do say eventually it will come back, but I can't find anything to suggest such a move any time soon
MICROGAMING AND USA CASINO PLAYERS
Top Isle of Man based gambling software provider Microgaming announced that from November 10, 2008 it would not service American players. This is due to a Kentucky Circuit Court judge threatening to confiscate the globally accessible Internet domain of Microgaming.com.
Online casinos powered by Microgaming software, have subsequently announced that they can no longer accept US players due to a lack of clarity around the US anti-gambling legislation (which is a dog's breakfast, and in reality all about taxation).
Players from the USA will not be able to download the casino software
If you're American, and do not already have a casino account with a Microgaming Casino, you will be identified as a US resident (via geotargetting your IP address) & will unfortunately not be able to download the Casino software or even view the download page. If you try to "work around" this geotargeting using a proxy tool to block your IP address, the casino will not be able to pay out any winnings to you (ie so don't bother!)
We're sorry things have got so bad for Americans, especially considering this is all about "tax take" rather than the actual illegality... so much for freedom of choice.
Once things are clarified in law, it is likely that many of the Microgaming Casinos will re-enter the US market - and it will be business as usual. It just takes time.