Some factors for US's continued growth: healthy demographics - due to immigration, low corporate tax rate, interest rate rising and dollar strength - attracting capital inflow, biggest economy in the world, biggest consumer market in the world, one of the most innovative for its size, balanced economy (used to be dominated by manufacturing, but now it is pretty spread out and consistent), good environment for rich to immigrate to, growing reshoring of manufacturing, leader in technologies, etc.
Instead of comparing US to the yesteryears, let's compare US to other countries in the world today and see why money is going to keep flowing into US for a long time.
Japan: seems to be on an upswing, the recent news of bring in 500,000 immigrants will help with the economy. Unfortunately, it still suffers from demographic decline, innovation staleness, 1.0% anemic gdp growth, competition from cheaper Asian countries for manufacturing, etc. Its paternalistic culture doesn't help to introduce women into the workforce and boost/diversify its economy. Still, a good place to live for many, and high standards of living. but not for investments.
Xi Jing Ping: he is the dictator, therefore he is the country and the economy. Sadly, history has proven that a society cannot escape middle-income trap until it has transformed to a culture that promotes openness and innovation, something that a dictatorship has never shown to do. Therefore the country is dedicated to stealing IP from other countries and companies for a long time. If one looks at other dictatorships in the current era, they always exhibit faster economic growth than their democracy counterparts. However, once the easy growth is used up, the dictatorships are stuck in a decline. As evidenced by the country's 350%+ GDP to debt, 3 trillion of its 6 trillion wealth has fled to overseas, and 50% of rich wanting to leave. Also, evidenced by strict capital control, draconian rule of law, censorship, housing bubble bursting, fake GDP numbers claimed by many of its provinces, etc. The current government will try to hold on for another 10-15 years, stunting the economy. Xi Jing Ping will die, then the grab for power will throw the economy into chaos.
EU: several of its nation members are suffering EU withdraw symptoms. Greece would like to leave but its economy is too small to matter. Italy however, is another story. With the 3rd biggest economy in EU, and the recent elected populist leaders, Italy will try to pile on the debt to address its anemic economy and migrants issue. EU unfortunately won't be able to do much; threaten Italy with debt reduction (currently 120% of gdp), and Italy will leave EU. Do nothing, and Italy will bring down EU's fiscal health until EU disbands. EU doesn't seem to be viable in 5 years.
Emerging Market: current capital outflow indicates there are trouble brewing due to expatriation of dollar back into US. From Turkey to Argentina to Indonesia, the emerging markets are going to struggle paying back their dollar-denominated debts with the rising interest rates and stronger dollars. Flashback to 1998 Asian crisis.
Disclosure: I have no stocks in play.