Airplanes exist. The network of infrastructure in Europe isn't just trains...
Part of the problem in North America is that there's not adequate public transportation from airports to city centres (whether it's a train terminal or frequent buses), not enough trains from city centres to suburbs/outskirts and not enough buses in between or from town to town.
I recently went from Paris -> Prague as an example. So I walked from the hotel in St. Germain to a metro station, took the metro to the airport, hopped on a plane, landed in Prague, then took a bus to a metro terminal and the metro to downtown Prague. That's what it looks like. You could have the same in the US... I haven't spend a ton of time there but the airport I'm familiar with in Canada, YYC (Calgary) has terrible access to/from the airport. The cab industry basically has convinced the city to not run a train line to the airport, nor to have a proper bus schedule. You need a taxi or ride for no good reason.
You can do that in the US, you can't do it everywhere, but for the cities on the level of Prague and Paris you certainly can. Most of the major cities on the east coast and West Coast that's applicable and for Chicago.
Philly, DC, NYC, Atlanta, Boston, Chicago, South Florida, LA, and the Bay area I've done entirely public transit trips many times to the major areas and that's covering a population larger than any EU country.
Part of the problem in North America is that there's not adequate public transportation from airports to city centres (whether it's a train terminal or frequent buses), not enough trains from city centres to suburbs/outskirts and not enough buses in between or from town to town.
I recently went from Paris -> Prague as an example. So I walked from the hotel in St. Germain to a metro station, took the metro to the airport, hopped on a plane, landed in Prague, then took a bus to a metro terminal and the metro to downtown Prague. That's what it looks like. You could have the same in the US... I haven't spend a ton of time there but the airport I'm familiar with in Canada, YYC (Calgary) has terrible access to/from the airport. The cab industry basically has convinced the city to not run a train line to the airport, nor to have a proper bus schedule. You need a taxi or ride for no good reason.