In this alternate history, the so-called Meiji Restoration is taking a lot longer than expected.  The kami have awoken to defend the islands of Japan from the pollution of Westerners.  Only machinery seems resistant to the influence of the kami, so the United States has spent years developing steam-powered clockwork military machinery to resist the occult powers of Shinto priests and wire-fu samurai.  This is like the  Un-Conquista 200 years ago, and we all know how that turned out.