You need to make a fair comparison here because did the services in Finland or Sweden already exist albeit on antiquated old lines? If they had an old line already performing those services then there's no chance that they'd build a separate competing line purely for speed or even capacity.
It's worth noting that the trains that we do have aren't slow, the Virgin trains for example get up to 130mph. There is just no need for an alternative service on a completely separate line that just so happens to go a bit faster, that is the idiocy of HS2.
The reality is that people will choose the cheaper option over the faster option and I'll bet my house that once HS2 opens it's trains will be empty and the Virgin type trains will continue to be packed to the rafters. For other countries there aren't two options so it's not a fair comparison.