You can also force Googles language using the query parameter "hl". E.g. www.google.de/?hl=en returns English queries. That parameter is preserved through multiple querries, so you can use this in a bookmark and have multiple google language versions just a click away.
Not as handy as the DDG location switch, but still a sometimes useful hack.
As I'm German, that's actually where DDG has the advantage over Google. Most of my searches are in English, but sometimes I want to search for something here, with DDG that's just a single press of a button and I get German results. With Google I'd have to do multiple clicks.