Yeah, you are right. The total area of the US is similar to that of Europe but number of Hivers in Europe is much higher than in the US. So it´s easier to host these meet ups here.

Talking about the differences between US and European trains, have you seen this? :D Explains a lot I guess...
https://www.reddit.com/r/Damnthatsinteresting/comments/zml6fr/passenger_trains_in_the_united_states_vs_europe/