Hasn't it always been like this?
No. It has't been always like this. The turning point was the disintegration of the USSR. The Soviets neutralized any threats posed by the US and vice-versa. Right now the US is the sole super power. And that is bad news for the US citizens, as well as for other people.
If you ignore the conquest of the continental territory and the countless atrocities committed there, which most tend to conveniently forget, I think the "turning point" was when the US managed to overcome European influence all over the world (mostly having been restricted by the British navy). So, perhaps near 1900 with the invasion of the Philippines, which included terror, torture, indiscriminate murder, etc? (
http://www.youtube.com/watch?v=8UNV-L21mWs - an interview with Peter Kuznick in TRN)
EDIT: further, it's frequently forgotten that the "founding fathers", despite wanting to create a freer nation that those in Europe, didn't exactly intend on creating a true democracy either: you can take a look at Madison to get the point. Their idea was mostly to limit the power to landowners and other wealthy people, not the great mass of the population.