If you have that few settlers come into a continent as large, virgin and as rich as North America (compared to tiny European countries that had been exploited for millennia in most cases, with very few natural resources) it seems to me that the US standards of living should've been 10x what the rest of the world had, if you take into account that Europe suffered through two world wars on its soil (where the second one especially nearly destroyed it industrially for many years) the US standards of living should've been more like 50x higher for several decades afterwards.
By any metric you can think of unfortunately I don't see life in the US being 10x better than in the rest of the developed first world for the average person (life expectancy, happiness, schooling, health, ...), I mean, as far as you can find out the majority of personal bankruptcies in the US is due to medical expenses, where in the rest of the world getting sick does not automatically mean losing all you've worked for in your life.
Nowadays with the whole 'money = free speech' it seems the table is tilting even more towards large class disparities in the population, and a much bigger division by the haves and have nots. Despite this perversely, due to endless straw-manning by interested parties, a lot of people appear, from the outside at least, to vote for politicians that are actively out to make their life worse: it is of course quite hard to develop an informed opinion when large amounts of money, advertising and content are funneled towards muddying any issue and transforming it into either a partisan dilemma or a who-do-you-like-most uninformed decision.
The general culture of the land also seems to have an extremely strong sense of being defensive any time the country is criticized in any way shape or form, in all countries I've lived in or visited there is not as much animosity when it comes to recognizing their nation's shortfalls: ask any European in several countries, say, about bureaucracy or lack of competitiveness or the impossibility to fire people etc. etc. and you'll never hear the end of it, ask any American about health care (unless of course the ones that have gone bankrupt) and you will just get partisan talking points, these days usually about Obamacare.
The cult of "rugged individualism" that seems to permeate American society is good for some things (very low barriers to starting a business, for example, a feeling of personal responsibility, etc.) but unless it's tempered by some sort of "compassionate government" it is not conducive to having a harmonious society where yes, there are still differences in social status, but they are not as extreme, and there is no risk of anybody in one of the wealthiest nations in the world ending up destitute because their genetic luck ran out and they were in an accident or became sick with an expensive-to-treat condition.
The US might be great from a military power standpoint, no doubts about that, and from a 'can-do attitude' as well, but society should be about a lot more than who has the most money, who can make more money, it's should not be a competition, as much as the gospel in the US seems to be that we are all born equal we really aren't: our parents' social situations are different, our genes are different, many of us have disabilities, everybody should not be held to the same standard in a win-or-die kind of situation.
People should stop thinking "I don't care if by doing X to prevent 'abuse' by that moocher society will be worse for everybody, as long as there are no 'moochers' it's totally fine if everybody is in misery but the really lucky ones", but the odds of that happening are pretty low, when interested parties will do their best to frame all policy decisions in a "you're against the 'moochers' or you are a 'moocher' yourself".
The best country in the world would be a country where everybody has the opportunity to excel, and nobody runs the risk of failing due to its inbuilt safety nets, the US could certainly afford this if there was the will to make it so, now that would be American Exceptionalism I would gladly stand behind.