I'm not so sure manufacturing is the panacea to all this. It might be like saying 100 years ago that we "need to bring farming jobs back." With 3d printing, robotics and AI, the need for human labor in manufacturing will be way down. Manufacturing was a 20th century source of jobs the way agriculture was a 19th century source. Facebook, Google and Twitter didn't make most of their money from manufacturing, for example.
I never said America would be gone. Most former empires still exist: Greece, Rome, Austria, the UK, Spain, even Persia. But I think the days of depending on American strength are over - it's not wise for any country to leave its defense in the hands of another country, especially an unstable or unreliable one. It's also not healthy for the world that the US has so much power, as they are increasingly abusing it.
My own opinion is that the US is pretty much guaranteed to turn to Marxism and worse unless there is a large subset of libertarians among the youth that I am unaware of. Historically, almost all countries decline the same way. They don't get their freedoms back unless there is a total collapse of the system.
I think the whole world is headed for a dark period. The US will certainly emerge much weaker, some countries will emerge stronger. Many nations will break up. I just hope we don't see horrible wars. There really aren't any advantages for countries to invade neighbors, but that doesn't mean it can't happen.
