Last info that I've got was that in New York mainly operated brigades with ties to Solntsevskaya and Izmailovskaya, this was from a guy who did time in US who I know personally. Then of course the latest are the Georgians from Razhden Shulayawhich were brought down. Shulaya got 45 years if I remember right. Then there was another brigade which leader is Aleksei Tsvetkov, but he is prison as well now.
They're into everything that they can earn from. Very rarely, you will come across groups which are into only one thing. And these groups probably will be either car jackers or credit card fraudsters in most cases.
I doubt there is one person in charge. Mostly the groups which are under Thieves in Law, will answer to them, but there's not one main leader in this group.
I would say they operate in a lot of areas. Brooklyn might be as the main area in the 70's till 90's. But there's lots of other groups in other states in US, like Florida, California, New Jersey, etc.