America did have periods of great and general prosperity in the modern era, especially after WWII. It was based, though, on other countries in Europe having been wrecked by war and taking a couple of generations to rebuild. America led the world as a producing and consuming nation. It still does, but not in the traditional ways of bashing metal, as it did. Instead, America is a high value producer and to work at the high end of its economy requires an education that many Americans either do not value, or are too lazy to get. Having prospered easily in the 50s through the 70s, many Americans, in my view, became lazy. Hard work is no longer looked on as an essential American characteristic.
Instead, many Americans want it all, but easily. They believe the mythical American Dream is their right. That is why they voted in a man with a gold-plated bathroom. They think he can make them all rich. They are as unfortunately stupid as he is.