People
America may be unique in being a country which has leapt from barbarism to decadence without touching civilization.
— John O'Hara

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
This is a sardonic take on a nation's history: it supposedly skipped the refined middle stage and went straight from rough beginnings to overindulgence. The joke lies in the missing step, civilization, treated like a station the train never stopped at.
Context reviewed