A fascinating new study looks at whether the US will remain the dominant superpower in the next century.

Many of James Kurth's recommendations are pretty mainstream, suggesting that America's dominance has been built on military power which itself is dependent on economic power. He points out that this has been based not so much on industrial strength as constant innovation. He says that to continue this into the future, America has to emphasise research into green and bio tech, and new medical and health treatments.

This emphasis on the future of technology pretty much mirrors the priority of the Obama administration which also stresses medical research. I am hearing that some executives of medical companies are arguing the administration is undermining its own objectives by taxing just such products.

But that's a digression. Kurth's most striking argument is that it's time for America to grow up. He directly challenges the idea that America benefits from "soft power" - the worldwide appeal of its ideals and culture. He says the projected culture is adolescent and damaging:

"It is usually forgotten that this popular culture is chiefly popular with the young - particularly those young who are still irresponsible, rebellious and feckless...If American leaders want to lead the leaders of other countries, they will have to act like mature adults, not like the attention-seeking celebrities of American popular culture."

Perhaps he's just spotted the difference between the heartland and TV-land. In my short time here, I've been struck by the tightly-buttoned, exaggerated deference, politeness and conformity of much of American society compared to its rather more free-flowing image abroad. But is Prof Kurth right that it is time for America to put away childish things?