Then your Googles left you astray. The US has been building Direct Reduced Iron furnaces which are used to feed arc furnace “mini-mills” (which the US also has

Then your Googles left you astray. The US has been building Direct Reduced Iron furnaces which are used to feed arc furnace “mini-mills” (which the US also has been building). The US has NOT been building new coal-fired blast furnaces, instead doing DRI furnaces (including hot briquetted iron) and mini-mills. Mini mills are flexible and can use DRI, HBI, and recycled steel as input (usually in the US they use recycled steel scrap primarily as input as it’s cheaper). DRI/HBI furnaces use a mixture of hydrogen and CO. So they already use hydrogen, but it comes from natural gas. However, this input mix of hydrogen and CO can be changed to be almost all hydrogen (almost CO can also be made electrolytically from CO2, as NASA just did with the Perseverance rover on Mars).