Are you a US citizen? And if yes why centralize the ban, why not make it known where the ban you think that it can happen, US isn't the whole world you know, but even at that I don't think with the adoption greater than it was in past, that the ban on bitcoin would materialize,
While US isn't the whole world, let's not forget they're a world power and what ever they do has a major impact on that section of the global economy. If the US government was to successfully ban bitcoin (which is quite impossible) the rest of the whole would follow suit especially those nation that has a strong relationship with the US government or rely on them for aid).
Agreed, if the US government stance is against Bitcoin others country will follow but it good that US is a country that love innovative technology and they also understand if they are against crypto while some countries legalize it while crypto manage to be successful it may somehow degrade their power.
Aside from that, the US and other country can not totally ban Bitcoin they can only place some restrictions (just what happen in China, Nigeria, India etc) cause they don't have control over Bitcoin.