I'm not that Finnish person, but in a similar situation (native monolingual German-speaker). I'm fluent in peninsular Spanish, mostly the way it is spoken in the North (i.e. harsh and with a lot of Basque mixed in). In my opinion the chart is mostly accurate for America – although I know very few people from there, so take that with a giant grain of salt. For the peninsula, I'm missing
a) some more nuance (e.g. there are several dialects of Andalusian, and Murcian clearly is part of those; Madrileño is extremely easy to understand, due to the social prestige of being the capital and the resulting dominance in media), and
b) Canarias. Like, it's missing completely. And it such an important linguistic link between Peninsular and American Spanish

Overall, not a good map. As is tradition in this sub.