The northern European countries all seem to have similarly styles dresses, with the variation mostly coming from patterns and colors. I can't really do justice to the variety of clothing found in a particular country but the examples should hopefully be good enough. I've also included examples from northern countries that are geographically considered to be outside of northern europe, such as Poland and Germany, which are in central europe.
They seriously blandified Cloud's mom's design in CC. It doesn't really match up as well with the above examples as he original dress does, though the simplicity of the design makes me wonder how detailed it'll look in the remake. I can't read the Japanese text on her artwork by I recall mention of her surname having been Strauss at some point, which is most definitely of Germanic origin.
As for architecture, the British Isles seem to be considered part of northern Europe. Denmark seems to have that kind of house as well. The church
seems to be of Gothic design, which was common throughout a lot of Europe. Gothic is actually a term associated with Germanic people.
Other things to take not of in the Kalm images is that in the first, you see people wearing small headbands, some of which have leaves sticking up, which is better seen on one of the passersby in the third image. Next to that person is someone wearing a wreath of leaves, similarly to the necklaces made of the same. I also spot what appear to be wooden beer kegs next to a bunch of metal pots and colored bottles. Also, considering the particular pattern of Kalm's cobblestone, it might be possible to trace that pattern back to a particular country.
While stuff like the balloons is somewhat generic and only really gives us an indication of what they're celebrating, the dancing and accompanying music are distinct. The music features violins and accordions, both of which are often used in folk music. The dancing involves a lot of leg movements, especially at the part not long before the change to an overhead view of the dancers.
Regarding the walls, there seem to be a lot of walled cities all over Europe. Not all of them have the kind of architecture that does that blocky thing with the upper edges. I'd need time to figure out which countries have the ones that fit best. The thing is, Germanic cultural influences doesn't automatically mean Germany or Austria is the main influence. Northern Europe is primarily Germanic in heritage, while central has a lot of Slavic as well. I'm aware it's probably impossible to pin down a specific country but it's fun to see how much we can narrow it down.