Well, this time it's America's turn! In order to get the free game, you need to register a 3DS XL console to club Nintendo between March 21st and April 30th. On top of that, you must also register either Pokémon Mystery Dungeon: Gates to Infinity or Luigi's Mansion: Dark Moon.
If you already have Professor Layton and the Miracle Mask, you can also choose one of these games:
Source / Details: http://club2.nintendo.com/3ds-xl-promo/