[Klarna] Why does the «Sales countries» block in the dashboard not contain the options for USA and United Kingdom?

USA and United Kingdom are supported merchant countries, so why are their options absent in the dashboard?

See also:

I have got an answer from Klarna support:

The account you requested does not work on the V3 server, hence not on UK & US.
Please see the developer site for UK & US respectively on more info how to set up a test account for the UK, and US.

Another answer from Klarna support:

US/UK is on a separate platform, so your test account does not include these regions.
Please reach out to a salesperson for an eventual agreement in the US/UK and you will be provided with a test account.