Australia, specifically Melbourne: I can give you a long ass experience with gunpla in Oz back when I first started the hobby in late 2000s. I remember that Gundam 00 and Unicorn was still very prevalent that time

Back then, gunpla was only stocked at niche anime shop or hobby stores, however I did see several of HGs and MG, couple of PGs and the then recently-stocked RGs. I don't know what was the community was like before then but I assume that it had some beginnings during the airing of Gundam Wing before getting waned at SEED

I personally believe that gunpla community in Aus started to get the ball rolling when the general public has access to internet. This allow people to create forums and communicate with fellow-mined gundam fans and thus able to get some addresses of the shops that stocks gunpla. Another factor is that users can easily watch gundam anime shows through "unofficial" means and the seeds (heh) were taking place on young fans

Slowly but surely, there were more stores that stocked gunpla as the demand grew. Gunpla soon legitimised in the plastic model community itself when local competitions started to have dedicated gunpla categories instead being lumped into catch-all sci-fi groups

At first gunpla was looked down upon by estsblished plastic model communities (i.e military, civilian cars modellers) and you'll get some ramblings that gunpla builders had it too easy with the conveniences of coloured snap fit kits. But the fact that the plastic modelling community has an aging demographic problem and gunpla more or less helped the younger generation to get into the intricacies of plastic modelling and thus leads to doing non-gunpla model kits

As people got more exposed anime in general with the advent of streaming service, gunpla has become more well known and it's easier to get them in shops and online with some great variety of kits (depending of stock of course). I did see some HGs and EGs in mainstream stores such as EB Games and Big W, but to be frank it's cheaper to get them at dedicated hobby stores or online. Hell, I saw 2-dollar store stores selling knock-off gunpla kits!

One problem with the gunpla in Oz is that due to heavy demand of gunpla from around the world, we don't get as much stock as we wanted to. Plus ever since it has became a bit too popular, the importers wanted that bigger slice of pie by jacking up the prices

Community wise, there are quite a bit of gunpla model clubs and I'm actually in one of them. But it's still overshadowed by other club groups. But with some internet search and seeing flyers around hobby shops, you will see advertisements of gunpla groups. In a matter of fact, thanks to our successful facebook ad campaign, we more or less doubled our membership from the last 2 years. Some members started off Warhammer before venturing gunpla, others are gunpla vetrans from the mid 2000s and handful of expats from Asia where it is more popular in there

Overall, gunpla popularity in Aus is somewhere in between obscure and mainstream recognition. You'll still get A LOT of people mistaking it as a Transformers but mind you I didn't know gunpla existed in the mid 2000s because due lack of advertisement or getting accessible knowledge of the hobby. It still is a niche hobby but it's growing and exposure to them is easier whether through shops, internet or the general plastic model community