The Golden Era of American Greatness occurred in large part thanks to the highest taxes in U.S. history, as shown in the graph below . Those taxes paid for an unprecedented national infrastructure, massive technological innovations, advanced education, a relatively effective government, social programs to stave off another Great Depression, and the most powerful military forces in human history.
Those sky-high taxes were mitigated by a complex system of exemptions. Taxpayers (corporate and otherwise) who invested money back into the country – and who thus sustained the economy and society with methods other than government tax-funds – could lower their taxes by directly investing in American goods and services.
When you hear stuff about America having “the highest tax-rate on earth,” 1) that’s factually incorrect, and 2) that base tax-rate DOES NOT INCLUDE EXCEPTIONS. Once you figure in exceptions – a task for which any CPA worth that name is trained and hired – that base tax-rate can drop to $0 or below.
Sadly, the federal government government kept the exemptions while – ever since Kennedy – continuing to lower the tax-rate upon which they’re based. That’s how so many corporations and wealthy individuals (like President Trump) can pay zero taxes and/ or get millions of dollars back from the government as well. 
Meanwhile, those same corporations and individuals continue to utilize – even destroy – the infrastructure and resources that are supposed to be tended with those taxes.
Anyone still wondering why the U.S. infrastructure is falling apart while our government maintains perpetual deficits?
Here’s one of your biggest answers.
1 – One of the other major reasons for that post-WWII “greatness” involved the aftermath of the War itself. Almost every other industrial power on earth had been bombed to pieces while exhausting its resources and suffering devastating losses to its work-force population.
Meanwhile, the United States, Canada, and other geographically protected combatants like Australia and New Zealand had high-functioning factories and an able-bodied work-force. While most of those other nations – being parts of the British Empire – helped to rebuild the British economy  the United States supported only itself.
Diplomatic arm-twisting also “encouraged” other nations to “buy American”… or else. Thus, the post-War American prosperity was unsustainable to begin with. Still, the high tax-rates and heavy investments in American goods and services propelled America’s greatest era. Without them, that era is a fading dream, nothing more.
2 – In fairness, those organizations and individuals still pay state and local taxes. That helps somewhat with regards to sustaining the local infrastructure, but does zero for the elements of social infrastructure and resources that are sustained in part or in whole by the federal government… which are actually quite extensive.
3 – An economy also sustained by Great Britain’s then-colony India, which despite geographic protection from most of the fighting lost roughly two million people to famine and disease during the War because the British Crown demanded ruinous support from the nation… a demand that led to India securing its independence shortly after WWII.