Captain America stands for the American people, the American ideal, the best of us. He does not stand for the current government, or any government. He does not represent the policies, the economy or the global viewpoint of the American government. He represents what America was founded on, not what it has become. Exploring this in his movie, where he finds it difficult to be a beacon for how the world and how America has changed since he stood up to fight for what was right, is the emotional angle they should aim for.
When someone screams "USA! USA! USA!" nowadays, its sadly more often than not a proclamation of American power. Cap is not a symbol of that - and that is what this movie needs to promote. So put him in bright colours. Because the American flag is not the American government. The flag is the American people. Hell, I'm British. But until they find a good avenue for the Captain Britain movie without cocking it up, Captain America's a fine example of what a person to strive to be like, regardless of the flag draped on their uniform.