A hypersonic missile, by its very nature, cannot make sudden turns or course deviations, no matter what the Russians and Chinese try to claim. So, presuming you can detect and track them in time, it seems the easiest and cheapest way to defend against them would be to launch a spread of high-speed defensive missiles with warheads designed to explode and spread a cloud of shrapnel ahead of the incoming hypersonic missile. Rather than the old “hitting a bullet with a bullet” approach, just make them fly through an impenetrable cloud of debris.
Lasers