He is being claimed by both.
The British press are hailing him as the first British winner of the U.S. Open since Tony Jacklin in 1970.
The Irish are hailing him as their own, the next great Irish player.
He is now in the frame with Padraig Harrington and Fred Daly, as one of only three Irishmen who has won one of the four major golf tournaments.
McDowell is an Ulster Protestant, who plays under the flag of Northern Ireland.
He talks of himself as Irish which he did when he won the U.S. Open and described how much the Irish fans on the course helped him as he endured that tension-filled final round.
It is doubtful if McDowell thinks too much about his identity and he is comfortable being described as both Irish and British.
The NBC coverage clearly pegged him as Irish and he seemed pretty comfortable with that.
His Northern Ireland teammate Rory McIlroy is a Catholic and also describes himself as Northern Irish first.
He said he was happy to play with Great Britain in the Olympics when golf is introduced, a comment that did not endear himself to many Irish.
McDowell seems to have no such identity problems.
He is a Northern Irishman, pure and simple, which makes him both Irish and British.
It is an identity he can be very proud of and both Ireland and Britain are very proud of him.
That is how it should be.