[complexmango]

The United States was once a 3rd world country that lost 10% of its population in the American Civil War. Within 5 decades of that, it produced 50% of the worlds manufacturing output.

Needless to say, Europe was it its peak at the time, and has only declined since.

Excuses are easy to come by - root causes are more useful to examine.

[hollerith]

The US was the second country to industrialize (Britain was first; France third) and that industrialization had been going very strong for many decades before the start of the American Civil War. Also life expectancy, infant mortality, adult height and similar measures were better in the American colonies than in the most advance Western European countries a century (and probably a century and a half) before the start of the Civil War. So I don't agree that it was a 3rd-world country at the start of the Civil War.

(I have no opinion on grandparent; I am reacting only to your choice of the term "3rd-world country".)