Currently, as far as I know there are the Westies in NYC. Hell's Kitchen section used to be an Irish immigrant enclave and still has some remnants left. The remaining Irish gangs are called the Westies. They are a nasty bunch. They've adopted the IRA use of 'knee capping' and they are used for hits by the Italian mafia. The Irish lost out to the Italian mafia in NYC during the '20s when basically whoever controlled the waterfront had the power.
For movies see 'State of Grace' and 'Sleepers' for mentions of the Westies.

Boston still has Irish gangs and the mafia (north end of Boston) has to do business with them because the city is still Irish controlled politically. Southie (south Boston) is where they are based, and a gang called the Winter Hill gang (not sure if I got the name right) was in cahoots with the mob and still do a lot of business.

Chicago's Irish gangs have pretty much died out. After Bugs Moran, the 'outfit', Chicago's Italian mafia pretty much ruled the city. (for movies see Millers Crossing which is based on the Capone/Moran rivalry).