The USA is a lot older than 70 years, so no the USA did not come of age in the jet era. It would be a lot more accurate to say that the modern USA came together in the age of trains, because it was trains that connected east + west together (+the bits in the middle). There used to be passenger trains between all major cities + many towns literally grew around the railways. That train infrastructure is still there, but now there are just very few passenger lines running on them.
The USA is a lot older than 70 years, so no the USA did not come of age in the jet era. It would be a lot more accurate to say that the modern USA came together in the age of trains, because it was trains that connected east + west together (+the bits in the middle). There used to be passenger trains between all major cities + many towns literally grew around the railways. That train infrastructure is still there, but now there are just very few passenger lines running on them.