You could, of course, keep both sides happy by including both flags. The text for each would be the same, with the following small exceptions. For the English-language version, every "o" should be followed by a "u", so you have words like "colour", "phoutougraphy", etc., that don't occur in the American-language. And for the American version, you should change every "ou" to "o", so that you get "color", "Photography", "shold" and "wold", and "Luminos Landscape".