It is possible. I just finished my first workout class on my Apple TV and I'm from Europe.
Open the App Store on your iPhone and sign out with your current account. Now you have to connect with a VPN service to a location where Apple Fitness+ is available.(I'm using USA) Now sign in with a USA App Store account. Open the Fitness app and the Fitness+ tab should be available. If not, close the app and restart it. From this point, you should be able to turn VPN off and still be able to see the Fitness+ tab. Your rings are still the same as always so no worries about that.
So now about the Apple TV, this is how I'm doing it:
I'm using my Apple TV over ethernet. Sign in with a USA App Store account on your Apple TV. Disconnect the cable and now connect the Apple TV with your iPhone's personal hotspot. This works over WiFi. Again, you have to be connected with a VPN first where Apple TV is available.
Once you have done this, the Fitness App should pop up on your Apple TV. From this point I learned you can reconnect the cable again and you're connected over ethernet. So you can disconnect the personal hotspot.
If you don't have your Apple TV connected through ethernet, you might want to download the lessons local on your iPhone and Airplay them to your tv since the 30 minutes workout video's are 1,5gb of data. I tried this and this worked too.
I few times the video's didn't show up because of an error, so I had to restart my iPhone/Apple Watch and after that it worked.
This is the workaround that works for me so hopefully other people can use it too now in Europe.
If you're using Apple Music, and you have music downloaded offline, it will all disappear. This since you're connected to a USA Store account. I also think your Apple Music will not be working. You have to be sign in with your regular account. But once you do this, the Fitness tab will disappear.
And about your free trial question, I can not help you with that. I have 4 months of free trial since I bought me Apple Watch 6 in the USA in September.
Hopefully Apple will not read this and blocking it haha.
Merry Christmas.