I'm not expecting to have them be similar numbers. My original point was purely anecdotal - I usually take 1-3 Amtrak rides a year and I don't even live in a part of the country that has good Amtrak service. It's odd to me that folks in a country with much better service use it less than I feel like I would use Amtrak if I could.
I'm pretty sure many Germans don't use the ICE at all. While service is a lot better, the way to and from the high-speed train station often makes it inefficient, especially because the German autobahn is also world-class and doesn't suffer from a "last miles" problem.
As a general example, the Midwest is roughly the same size and population as France, so if we made the investment we could reasonably have a regional high speed network centered on Chicago. We’ll never have coast to coast high speed rail, but having a few regional networks is certainly doable.
Amtrak had 31.3 million passengers in 2016 [1]. That's 0.095 passengers per capita. And that's on all Amtrak trains, while the German number is just for the ICE high-speed trains. Amtrak's high-speed Acela trains only had 3.5 million passengers in 2019 or 0.01 per capita. [2]
Per capita is just not a useful number for this discussion.
[1] https://www.amtrak.com/content/dam/projects/dotcom/english/p...
[2] https://www.statista.com/statistics/1155658/acela-high-speed...