My opinion of Americans before Obama was that they were all fat, stupid, drugged up, racist, neighbour-hating, religious fanatics who are patronising towards anyone British.
Since Obama, I think they're a bit less racist.
By the way, Britain already IS hated by everyone else, and we hate them all back! We just happen to be so tolerant that we bloody well put up with them. For example, England had to put up with both Scotland and France for 600 years. Even terrorism. I have 2 friends who live in London and use the Tube trains a lot. After 7/7, they got straight back on the Tube as if nothing had happened. I don't remember much from 9/11 as I was 9 at the time, but almost every single American was completely hysterical about the whole thing and even to this day a lot of Americans are still paranoid about terrorists.
The biggest thing about America I hate is that they provoked these with both Gulf Wars. The first one (1990) was justified. The US wanted to rid the Middle East of all the weapons that THEY HAD GIVEN THEM during the Cold War.
Then, the second Gulf War (2003) had no justification at all. Bush said that he had recieved intelligence indicating weapons of mass destruction and invaded Iraq, bringing us into the war with him. When they found no weapons, they then went looking for Saddam while big oil companies rolled in. The war MAY have been to dispose of Saddam, but it wasn't any other countries business what the state of affairs in Iraq was, so I think that the whole war was just driven by a greed for oil.