I don't know about Sweden and even less about the US, but in France, for example, it's illegal to send cash via mail.
Not sure what would happen if they caught you.
Not sure what would happen if they caught you.
Where the line in between lies, I have no idea.
I assume it’s to avoid responsibility and money laundering.
From what I see there are limits on the amount of cash you can mail in the US as well.
In reality, nobody gives a fuck if you mail someone 50 euros.