Man you picked the right company alright. Nintendo's impact on Japanese , North American and European cultures is off the hook. You could use the most used story in gaming history. The great crash of 83, when all the game companies began to go down. If it wasn't for Nintendo their would be no video games industry like that of today.
Nintendo formed our video game culture, almost everything you see today was started by Nintendo. You could use the more recent cultural impact the Nintendo Wii. The Wiimote changed the way gamers around the globe game. Now thanks to the Wiimote game companies are giving us active gaming, the motion controller (Move,Kinect) would not exist if Nintendo hadn't pioneered the technology.
Or how about the DS's impact on North American hospital's and in our cuture. Thanks to BrainTraining and other games that supposedly help your brain, DS's are now in hospitals and retirement homes across North America.
Or how about how the GameBoy line-up formed Cell phone's of the day and our cellphone gaming culture. If it wasn't for Nintendo Nokia would have never tried with the N-Gage and the I-Phone today would probubly look alot different. But because Nintendo pioneered handheld gaming we today have cell phone games.
Also don't forget WiiFit which has helped our culture in being more active. WiiFit sold about 10-million copies in North America. It started a major fitness fad which has changed millions of lives. It also has shown people that games aren't only good for hand eye co-ordination that they infact can help your health in many ways. This revolution has led to about a dozen other fitness titles. It has changed the way we look at games which inturn has changed our gaming culture and the cultures of the world.
Or how about Mario who today is more widely known around the globe then Mickey Mouse. Mario and Donkey Kong for example helped form our generation and the preceeding one.
There are so many culturally impacting points you could use, I'd be happy to help you out with facts if need be. But I think it'll be easy for you to do yourself.