Because USA is too large. Come to Tokyo and Seoul where people are a lot more concentrated. Those pictures are from Tokyo.
I mean it's not because USA is behind, just difficult to find all the latest technology products in one place which is often the case in Seoul and Tokyo. Most tech things are easier and cheaper to buy in the USA than in Japan whether online or offline.
That Akihabara market is used by many of the best Japanese electronics makers to test the market before launching in the mass markets of the world, but also by companies from overseas like LG, Asus, AMD, and so on.