Look forward to people replying to this question!
Yes, the USA introduced more and more emotion into their haiku, while perhaps British (England, Wales, Scotland) might be less subjective, with much less emotion.
Japanese haiku (1890s onwards) is varied, with multiple schools, from basic shasei (stage 1) through stages 2 & 3. Many are similar to hokku and other haikai verses pre-1890s and would include a classic, traditional, or authorised kigo. Kigo often require to be "re-authorised" yearly, so new kigo might be trialed through the year in journals, and then there is the anticipation to see whether the major saijiki (kigo almanacs) incorporate them. Sometimes a kigo published one year is dropped the following year or following years. The seasonal aspect to haiku in Japan, through designated kigo, is still a main feature of haiku.
Other schools in Japan might either do ultra-contemporary, gendai, non-kigo, or a mix. Folklore and mythology are of course strong in Japan and their language systems (plural) allow for much more content and whole quotes from poems etc...
Eastern European haiku were famous for explicating the wars when Yugoslavia broke up, with intense realism rarely seen before, even in anti-WWII haiku from Japan.
Check out
hadaka: all that comprises life:
https://www.thehaikufoundation.org/forum_sm/index.php?topic=2130.0With the internet, Twitter, and Facebook, for starters, people from various countries would expand their approaches. African haiku is often interesting because they focus on their national or personal culture:
https://www.thehaikufoundation.org/omeka/files/original/45bbf38ca68bb214b04e4476bdb0b9a2.pdfI've witnessed from India over three decades, where they struggled with moving aside from their world literature supreme epic poetries, into 'pocket' verse such as haiku and senryu. Dr Angelee Deodhar and K. Ramesh (male) were frontrunners and slowly slowly Indian haiku became world-beating and world-winning haiku dominating global haiku.
Now for the last few years it's been African haiku, and I was involved years ago with the Kenyan wave of haiku, not always seen globally, but despite all the odds, coming through. Now Ghana, Nigeria, and other African countries are strong!
Who knows what country from Africa, or an entirely different continent is next? And of course most of us only read haiku in English, and not Romance languages (France, Italy etc...).
There'll be a wave of Urdu poetry, from Pakistan mostly, coming soon. Stay tuned!

Perhaps parts of the U.K. such as England, which is quieter place for haiku in comparison with Wales and Northern Ireland? Scotland also had strong haiku writers who have either passed away, or stepped down.
As Marion Clarke is from Northern Ireland, I'd love to hear more about that part of Ireland!
Alan
I would appreciate insights on the differences in haiku of different countries. For example, some of Japanese haiku have a surreal tone which is not present in the haiku in United States. The haiku in United States focus on emotional resonance while Eastern European haiku have an incline towards the mystic and nature. I've also observed that Indian haiku are social in nature. I would appreciate your views on this.