I am not sure about the United States, but there are hundreds of Bitcoin exchanges based there and I believe that it is quite easy for the Americans to purchase Bitcoin. Anyway, for now we can ignore the US. What about Japan? Don't tell me that it is easier to purchase Bitcoins in Ghana (which doesn't have a single Bitcoin exchange) than doing so in Japan.
Not sure about Ghana <-> Japan comparison, but there aren't 'hundreds of Bitcoin exchanges'. The US has several of the big ones there, but that's it, the barrier of entry is too high.