That, its the #1 as far as military power and raw economic throughput goes (might be #2 now for the economy now with China growing and all), but when you start measuring it with other metrics (democracy, corruption, national debt per citizen, health care coverage, education levels, homicides per citizen, long term sustainability of the economy, dependency on fossil fuels, etc), it falls behind many other countries.
What really annoys me is the pervasive attitude of some Americans that their countries is #1, because with that attitude, they are less likely to look at the various things that are done better in other countries and learn from them.
Whenever I have a discussion with Americans about problems with the economy or the state of democracy or the environment, it tends to be held back by how willfully ignorant many Americans are about solutions to these issues that various countries came up with and successfully implemented.