To address your questions in reverse order:
No new country specific worlds are introduced.
They now have 3 variants that are used.
1) Forgotten Attacks with willingness/morale/forgotten boosts
2) Forgotten Attacks without the above
3) 'Classic' with no forgotten attacks but with willingness/morale/forgotten boosts
They are expected to introduce a Basic world with no Forgotten Attacks and no morale etc but no timeline for that.
They've also introduced Veteran worlds with a totally different scheme of scoring and aim.
Challenges have also featured over the last 2 years, although they may have been around before then.
As to what's been changed in gameplay, it is probably best to visit a world to learn. If you manage to join a good group then they will guide you on the differences. Wrath 18 would be a good place to start.