I don't think creativity and adherence to social rules lie along the same axis. Strictures can spur and channel creativity. And the absence of strong normative behaviors doesn't coincidence with greater creativity--there are plenty of countries, mostly undeveloped, where people generally do anything they want[1], but there's not much creativity going on.
As the rest of the world industrializes and the deficiencies and costs of our own social fabric are revealed in comparison, Americans seem to increasingly like to distinguish ourselves as "creative". But it's really just a euphemism intended to characterize our differences in a way that permits us to claim that we're "better" at something. Back when the U.S. was a leading industrial power house, when our democratic institutions were unique, there was no need to identify a specific quality like creativity to distinguish ourselves.
[1] I've been in at least one country where the very concept of a line seemed foreign to most of the people, who were within months or years (not even generations) removed from an nomadic lifestyle. This was qualitatively different than in some other countries with aggressive line jockeying and cheating.