The US Navy has already begun to abandon its plans for a railgun, $500 million spent, not anywhere close to being operational, another rube goldberg device MIC boondoggle to be cast upon the scrap heap of cost inefficiency.
Putting aside the fact that, strategically, the whole concept of war by bigger, faster firing, longer ranged guns; was proven to be folly in the First World War, the guns themselves also became too clever by half, so expensive and fraught with complexity, that not only did they not win the war, they bankrupted the co-belligerents in the process.
Any attempt by the Chinese to achieve decision by firepower would likely result exactly as it did for the Germans in the First World War, firepower stalemate, up to and including hydrogen bombs, followed by American led international naval blockade for the win, railguns et al; no stick there, strategic waste of time, effort, and money.
What's the rush? They've got all the time in the world, every Hegemon has an arc, just sit back, bide your time, and America will bring itself down from within, giving America a foreign threat to rally against is counterproductive, left to their own devices, Americans will turn upon themselves.