Purchase iTunes Match in countries that do not have it? Can I change to the US store in iTunes and purchase iTunes Match and then after the sync switch back to Swedish store in iTunes and still have access to iTunes Match?
Nope, you can’t. Also, you have to have a US credit card to use iTunes Match in Sweden. Even if you do find a way to sign up for iTunes Match, there will be problems. 

Once you switch to the Swedish Store, you will lose access to iTunes Match.