Whenever I've seen someone with completely white teeth, it has been an American. I have been absolutely amazed.
I have good dental hygiene. My dentist always compliments me, and I rarely have cavities, but even then AND brushing with an electric toothbrush morning and evening, my teeth are more towards the yellow side than blank white.
I heard that there is fluoride in the American water systems (but unlike the tinfoil hats I don't believe it's dangerous or meant to make people sick and reliant on big pharma). Since fluoride is good for your teeth, is that the reason? I don't think we have that in our drinking water here.