Nearly no place on earth would remain unaffected. Certainly not within the USA when it gets hit.
However , if you are thinking about a non-hit area and only minor affected by radioactive Fallout coming from places that were hit, yes there would be several places within the USA.
Everything that is far away from anything remotely important. Small rural towns far away from military installations , far away from any huge city, far away from industrial or logistical hubs.
The fictional town of Jericho, Kansas in the tv series with the same is the role example for such a place. A absolutely isolated place in the middle of nowhere would be a good place to live in case of a full nuclear strike on the USA. If you want to witness and live in the world that comes after that.
Considering that, it may be better to search oneself a place near a important military installation like a nuclear missile base or airforce base to ensure a quick and painless death taking no longer than a second. :nuke: