How to purchase a Mac Book Air with a keyboard from another country?

When buying online as mentioned you are given some keyboard language options. If Swedish is not available in the online store for the country where you are, then you may not be able to get the actual Swedish keyboard.

However, it is still possible to add Swedish input layout to MacOS through system Preferences, yes the physical keyboard will not be the Swedish layout, but will act as such. So typing a letter will produce the Swedish character that would otherwise be there in the Swedish layout.

link-> Type in another language on your Mac with input sources - Apple Support

If there is an Apple online store in your country, go to its site and pretend you are buying one. There will be a dropdown menu showing the keyboard languages available.

If Swedish is not there, then you will need to travel to a country where they do have one like that on the list (Apple stores do not ship outside their own country) or try to buy one via the internet from a non-Apple source.

Swedish keyboards are not available even in the US, so it may be difficult to find this in in your location.