A couple of years ago...
At any rate, it seems that many here are arguing the politics of the flag's presence in this statue, and either completely forgetting or completely ignoring the
ideals involved.
The most brilliant aspect of the whole Civil War scenario was the conflict between the two vastly different ideals represented respectively by Steve Rogers and Tony Stark. Rogers represented the purity of the American dream, as embodied by the country's "Greatest Generation." He stood for the purest interpretation of the United States Constitution, and its Bill of Rights, and the freedoms represented by those documents as laid down by the Founding Fathers of the U.S.A. (The "Death of Captain America" storyline was a bold metaphorical statement by Marvel, implying that the ideals, the America, represented by Rogers are dead and gone.)
Stark, by contrast, is representative of the industrial capitalism that later came to dominate the United States (and which enabled it to become the world power it is today). He's a captain of industry, an innovator, a great leader, and a designer of state-of-the-art weaponry. Stark is no less patriotic than Rogers. And while the two stand apart from each other in regards to their perspectives and interpretations of their country's ideals, Stark is just as much a symbol of America as Rogers ever was.
His status as an American patriot doesn't exclude Stark from being a citizen of the world, however. (We all know that he succeeded Nick Fury as head of the world peacekeeping task force, S.H.I.E.L.D.) I think it's pretty logical to assume that any of his dealings at a global level were influence heavily by his belief in certain aforementioned American ideals.
And why not? Despite how any of you may feel about the recent state of American politics, foreign policy, or what have you, it's hard to argue that, as it was founded, the United States is a great country.
So leave current politics out of it and look at this statue and its flag from an ideological perspective.