I would say that the most important city in the U.S. is where i am now: Boston..
It's probably the most historically significant, it's a world class city, we're commanly refered to as the cradle of western society, The Athens of America, we probably have one of the top if not the top universities there are, (Harvard), the best tech university, (M.I.T.) the best music school (Berkley), JFK was born here, John Adams and John Quincy Adams were born nearby, Lincoln love visiting, and staying. A galloping John Revere shouted "The British coming!" right by the state house here in,.. George Washington fought the revolutionary war nearby. It's been around since the 1630's, We've got the first underground railway system, (the green-line)Barack Obama use to live nearby and went to school here, Numerous presidents from the US president to other leaders of men and land went to school here. It's probably got the best hospitals in the nation (Children's Hospital, Mass. General Hospital) Hell i think even osama bin laden went to school here or has family here..I think 2 out of the 4 jetliners during 9/11 left from here in Boston.
We're definitely an important sports city. The New England Patriots won three Super Bowls in four years ('02, '04, & '05"😉 and went to the super bowl in '07) making them the best nfl team of the decade.
The Boston red sox won the world series in '04 and in '07.
The Boston Celtics won the NBA Championship in 2008 and will win it again this year cause they're 10x better than they were last year. (They currently have the best record.) So you could imagine being apart of that with this place being a college town as well and how crazy it gets..
But yea, that's all i could quickly come up with in my head for now..