The decentralised state system has worked well in the USA in the past. However, the rest of the world is becoming increasingly centralised, both in terms of government, but also socially - especially with the spread of mass-communication technology such as the Internet.
The USA, however, seems to have been very slow at centralising and, in my opinion, modernising. It is very provincial, with too much power devolved to state level. While one could argue that this produces more freedom for the individual, it must be considered whether it simply gives more power to those who run the state and to petty local interests which are not in the interest of the nation, or of progress. I don't need to remind anyone of the Creationism/Intelligent Design debates, or segregationist regimes during the late 19th century up until the 1960s. I believe that the provincialism of the USA stifles intellectual, social and cultural progress, and will cause the country to fall behind other countries in the future. The electoral system of the US, giving too much representation to states with little economic or cultural value, helps to cement this provincialism in US politics and things are unlikely to change without serious electoral reform. The rigid nature of the US Constitution makes this in itself difficult. While designed to promote liberty, the Constitution seems to be outdated and inflexible, and I conjecture that it will cause liberty to be lost in the long run. There is also not much of an independent national media to speak of in the US, which is yet another problem. There are no real national newspapers and most people seem to buy local publications, further exacerbating their insularity and lack of knowledge and understanding of the world beyond their state, let alone beyond the US.
The US is increasingly vilified by the rest of the world as it remains resolutely indifferent or hostile to change. We are moving on while the US stagnates, but with its power (notably built mainly on central authority - technological development, for example, is highly centralised) it can still exert a lot of influence over the rest of the world. This is becoming more and more resented as there is an increasing perception of the US as culturally inferior; a land composed primarily of rednecks and reactionary Christian fundamentalists. The US can look forward to even more deterioration in its relationship with other countries if it does not begin to change now, and shake itself from the chains of provincialism. I could bring up the threat of China, but I really don't think that's necessary here.
What do people think of this? Clearly my argument has flaws and is largely composed of my perception of the US, Europe and the reactions of different people to the US. However, it is not intended as a waterproof argument - I have composed it merely to provoke debate.
None.