The difference as i see it is that in america, blackface is always auto-racist while in Sweden blackface can be racist depending on the context of the presentation. The fact that a few people complain about it does not make it racist in itself. Everything would be racist if that was the case.
More or less.
Let me give you some facts that will help you in life.
Blackface is racist. Period. The percentage of situations in which blackface would be appropriate is so small as to be statistically negligible. The fact that Sweden just happens to have fewer black people around to make their voices heard about it does not make it less racist.