Or... Since this wouldn't discriminate hodling (nay, quite the opposite) then the outcome would just be felt at merchants... Many in the US would indeed stop accepting BTC publicly. (Poor bitcoin Sign industry!)
But let's face it. Merchant adoption in the US is abysmal. The rest of the world is where the good stuff is happening on this front. All these startup economies like bitcoin Beach, bitcoin Lake, Bitcoin Ekasi, etc... Those will all shine like a beacon to the whole world as they grow.
Americans who still want to use it will then be incentivized to use more permissionless tools. This part is very good for bitcoin. Ideal, in fact. It takes bitcoin back to it's cyberpunk origins in the mind of all americans.
The price may take a small hit at some point, but this really isn't unwelcome news.