Any badge on your nation page appears to contributed to a card rarity. The bulk of these rarities are determined by the volume and quality of your census stat badges. The actual thresholds of each rarity are not static; they're assigned as a ratio of all nations. 0.1% of nations will be legendary, 1% of nations will be epic, 3% of nations will be ultra-rare, 7% will be rare and so on. So the combined value of all the things on your page need to be higher than X% of other nations if you want to hit a certain rank. The weights of each badge aren't confirmed by admin, so it's largely guesswork based on what's ended up where in the past, and whether or not admin has changed those weights since the last time we saw a demonstration of them.
Some observations from S2's mechanics:
Somewhere around 32-35 1% badges for a nation to hit legendary without any other contributors (as far as I remember, it's been a minute)
It's possible in very very rare cases to reach "rare" with no gold badges of any kind, just loaded up with 5%s instead.
It's possible to reach ultra-rare on a founder-delegate combination alone if your ID is low enough. (all other things being equal, ties appear to resolve by ID, just like everywhere else).
It's not possible to be commended or condemned at get a rarity lower than ultra-rare.
In-game authorships (WA resolutions and Issues especially) have substantial weight. Founder has less, but still multiple 1% badges' worth. Delegate seems slightly less than that.
One gold badge, alone, is not enough to rank out of common. Two should be enough, however, and any founder badge will be worth at least uncommon.
How useful or relevant are these observations in July 2021? Hardly at all! An actual S3 is unknowable. There were 169,000 nations when the last season was created, there are 219,000 today, so a whole swath of players would see higher rarities on their nations than they would have last time. Perhaps admin has changed how things are weighted since then! There was some confirmation by [violet] directly in the card server that deck value at certain rank tiers would have a factor in S3's rarity. By how much, it is a mystery. There's just no way of knowing how things will look or how much will be changed from before.
Best advice for long-term gains on your card rarity, however, would be to just answer issues consistently the same way over a long period of time and grow your stats to impressive numbers.
The Python wrote:[*]Being delegate of a large region (such as a GCR)
There does not seem to be any indication that being a delegate of a GCR has more rarity weight than being a delegate of any other region.
Bran Astor, for example, was weighted approximately how I expect a nation of any region to be rated with a delegate badge, two 1% badges, and a collection of lesser ones.