Globalization has shrunk the world. Imperialism has ended and we must now compete with poorer countries for resources and markets. They will climb and given the limited resources we will fall. This is not a bad thing as the median wealth of the world increases and more individuals are educated peace will rain.
Things are pretty bad right now, but I imagine that things will get better over time. You can never predict the waves of history and it is totally possible that some new method or other technology brings us forward. We just don't know and it remains to be seen how events play out.
America needs to find a new niche. American youth are very resourceful and as soon as it is realized what needs to be done to help our economy, they will get together and work hard towards doing it. Besides this, the statement that all economic growth is behind is too fatalistic. Even in the worst of scenarios, a stock that trends downward has periods of increased value.
I won't pretend to be an expert on the economy but I know that it's current state is less than perfect. There is always room for economic growth, especially when things are considered to be doing quite poorly. As far as how we open up to make things grow, I could not tell you.