the USA has built itself the largest economy in the world, has more military bases worldwide than any other nation, and has since the turn of the 20th century inserted itself into other nations' affairs more than any country. It has used it's power to largely dictate most global systems. It was and remains the world's first and largest super-power.
So big surprise when there's a 900lb gorilla in the room that people spend a lot of time looking to that gorilla's behaviour, good and bad.
At it's worst, like Bush, the world suffers through the USA's influence and tries to get by, and/or ameliorate the damage. At it's best, the USA's global power has meant it can set a compelling example - ie that influence has been used for 'good'. Both circumstances have resulted from which driver has the head of the gorilla.
In Obama, the world hopes and craves for that good compelling example.
Short version - the USA has a lot of power, therefore the world 'looks' to how it uses it, via your leaders. In return for the power and the blathering on about a light on the hill, we expect a raising of the bar. "This can't possibly get more disturbing!" - Willow
The rest of the world has often got little choice as to how to react to US power. For instance the Irish Government acquiesced to rendition flights through Shannon despite the vehement opposition of the overwhelming majority of the people. The serious people tm in the elite calculate that the consequences of pissing the US off are worse than pissing off their own electorates, and democracy be damned. notes from no w here
