There is no such thing as a US version of the DX any more. The DX sold by Amazon is global. The old US-only version would probably not have worked in Sweden, as it ran on a CDMA network, not GSM, like the new one.
The books you can buy are limited by the country that your Amazon account is is, including what country your credit card is from. Many booksellers have geographic restrictions.
Edited to add: by the way, the DX does not have wi-fi. Check the Amazon DX page for details.