My concern and the reason I feel we're closer to what Moops said is that the American people are declining in their
We have a whole generation of snowflakes that are not cut out to compete globally with people from current third-world countries. Millennials from India, China, SE Asia, LATAM (IMO) are harder working and able to put up with the difficulties of life. (BTW, for a good read check out the book "The Coddling of the American Mind")
We have seen out we have become malleable to the boot of government in controlling millions of people. (Seemingly justified now with the pandemic, but, likely to be more easily done in the future for less real "crisis".)
And, we have millions of people who are all too willing to let "the government" take care of them. Free money is being handed out and we can see first-hand, in real-time that millions of people are willing to sit at home and collect unemployment instead of work. Without the work, we are not producing services and products that will sustain the economy in the intermediate and long term.
The above teamed with a general heightened animosity amongst groups (political, racial, economic) has weakened our unity.
The examples you gave of America's past triumphs over their era's issues, relied on moral, ethical, and communal resolve and unity. We don't have that as we did in the past.
Example: my mom, who grew up in the depression and was a teenager during WWII, recently talked about how different CV19 was vs. WWII. During WWII, there was no government handout to help communities like hers that were hit economically when 20% of the town left to join the military. There were no bailouts, not handouts. In fact, the citizenry was encouraged to buy war bonds. In the midst of their scarcity, they were asked to sacrifice for their country. They sacrificed their lives, their family members lives, their time, talent and treasure to support the country.
The past 14 months have not shown any sort of resiliency to match what happened in WWII (or, frankly, in other times of significant duress in the collective US lives). I don't relish in death of citizens, but, in short, "war" be it vs. another country or a disease, will have casualties. CV19 turned into "not one life should be lost" and it has created a weaker economy and a weaker moral/emotional backbone.
In short, we are not united as a people. We are not united in our resolve to work and sacrifice as was done in the past when great obstacles were overcome.