Yeah, while, in theory, I agree that Philadelphia is crucial to the story of America's founding... which other (more visually iconic) cityscape in the new lineup would you cut? I think the three big ones they picked kind of have to be there, too.
And I wouldn't have wanted them to go any city-heavier than they already did (because this is in The Land, after all, and should be more a celebration of the natural beauty of the country).