USA: Spanish. I’m learning Spanish, and I think as a whole it’s like 18% of people in the USA but I feel like you’re likely to encounter some Spanish speakers and make friends even if not everyone speaks Spanish here.
Brazil: It looks like Spanish is also the second most spoken language with 4% or English with around 5%. I’m sure you’re more likely to find people on the Internet who speak it.
French: English, apparently a quarter of the population speak it??? Not sure how likely you are to find someone in the wild speaking it, but on the Internet, a lot of people.
In Sweden you can get by with just English, no problem. A lot of people also speak Arabic or Finnish, but unlike English it is not taught to everyone in school so you can’t expect everyone to know it, or get by without learning Swedish or English.