I do not think they are or even operate out the USA so even if they did ban those customers from accessing their site, I do not think they will even respond to you since they do not need to now. According to their terms of service where they do not cater to US residents.
Just feel sorry for those customers that had a balance or recently won.
They will not be able to get their funds now they are not obligated to send anything, including emails or support tickets, to those customer in the States.