The US would need a president who is bullheaded enough to executive order a thing, like drop the penny or paper straws, but that also likes Europeans, so we might be waiting a while for a push from the US government. Printed media nerds, however, already know about benefits of A* and will switch as soon as they're in power and can spend the millions and millions of dollars it would cost their company to switch. Printed media is not as important as it once was, though, so the switch is really to start outputting PDFs as A4 and letting people print scale-to-fit when they actually need to print something you've sent them. Given how often my printer sees use, I doubt most people would notice if the PDFs you send them started being A4 instead of US letter.