This all comes down to a history of cheap passenger plane flights combined with geography.
After WW2 all these companies that were building military planes saw that there was a viable market for commercial airline passenger service in the US (compared to other countries) because:
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1) The US is very large and taking a train from NYC to LA or NYC to Miami is simply not much of an option (even with today's HSR tech the times are still unreasonable due to the vast distances). This is a unique geographical situation not seen in most other countries that currently have HSR systems due to their shorter distance needs allowing their trains to have a reasonable travel time for their citizens. (Note: Even China's longest HSR line only goes half the distance from NYC to LA)
2) Oil was dirt cheap in the US compared to most of the world so we could accomplish widespread airline passenger service without having incredibly expensive fares due to low fuel costs. (This is also seen in our cars where we have huge engines compared to most of the world due to our history of cheap gasoline). Hopping on a plane to go from place to place became the norm.
So while we built airports other countries built more rail service lines to crisscross their country because it was actually a viable option compared to planes due to their comparable short ride times.
BTW Airbus didn't really make a name for itself until much later. While they had a jet ready in the 1970's. I don't think they really got any traction until the 1980's. So basically if countries wanted a jet they had to wait inline behind the huge US airline demand.