Sony's Walkman finds success in Japan, but what about the US?

In a world where smartphones make the most convenient portable music players, the market for dedicated MP3 players has dwindled. That hasn't stopped Sony from hawking its once-popular Walkman line of PMPs, however, and the effort is slowly paying off, with Japan embracing its latest Walkman ZX1. The ZX1 was announced back in September 2013, going on sale in Asia …