The size of the country/states isn’t really the issue, right? You can cross Europe via train pretty easily, 4hrs London to Amsterdam, longer over land than Dallas to San Antonio for example, but I’d assume a normal life doesn’t regularly involve driving all around the state. Most of daily life is just within a city or region, the size of the country is irrelevant there.
There absolutely are major factors that basically force North Americans into cars, I agree, but I don’t think size is an excuse for those factors.
edit: This video talks about the ‘North America is too big’ argument in detail, but fair warning, the creator is a bit annoyed and crass at the start and talking about comments they get. You can skip to 2:30 to jump over it.