I'd add that the decades after WW2 were boom times for the Unites States. So many other industrialized nations were reduced to rubble. The effects of having to

I'd add that the decades after WW2 were boom times for the Unites States. So many other industrialized nations were reduced to rubble. The effects of having to rebuild lasted decades. Post-WW2 the U.S. made up about half the world's GDP - equal to all other countries and the planet combined. Things are quite different now. The Unites States makes up less than a quarter of the world's GDP. Those great factory jobs with pensions and benefits are long gone. That dovetails with your #3, globalization.