If the dollar goes to zero, and it costs a million dollars to buy a single euro (substitute with any other large currency), but I still own a bitcoin worth ~26,000 euros, then I will fare significantly better than if I owned no bitcoin.
depending on how much bitcoin you owned you might be ok but there's still issues to consider. for example, you might not have a job anymore. you might have to consider leaving the usa so you can get away from the us dollar and be free to buy those euros and use them...
as an altetrnative to owning bitcoin i suppose someone could own gold or silver. those are also inflation hedges.