It’s also largely a function of population density. The US has a population density of 36 people per km^2. France has a population of 118 per km^2. Italy is 217 and Germany’s 240.
You simply CANNOT offset that difference with mass transit of any kind. Passenger trains will NEVER be as cost effective in countries with a low population density as they would somewhere with a high population density even if they are cheaper to build there. Moreover, it is particularly sensitive to both the population and population density of the cities served. With a population of 10.25 million in the greater metropolitan area and a population density of 21,500 per square kilometer, Paris France is a near ideal terminus for high speed rail. By comparison, the greater Washington DC area has a population of six million people but a population density of only 419 per square kilometer. You are comparing apples and oranges.
Which makes California’s High speed rail route between Merced (pop. 83,000) and Bakersfield (pop. 380,000) particularly stupid.