Copernica is a large genus fan palms from Central and South America and the Caribbean.  It contains a large number of very interesting species, most of which are tropical and very cold tender.  C. alba, however, ranges into parts of northern Argentina that receive quite hard frosts.  It has been tried in the Southeast US and so far found to be intolerant of temperatures below -6°C/21°F.  However, it is possible that if seed were collected at the most southerly part of its range, such provenances would be found to be more cold-hardy.  Associated palms from this area, such as Trithrinax and Butia, are quite hardy.  I would not bother with plants of unknown provenance, and I would not try to grow them outside of the very mildest microclimates, and I would advise protecting them from frost when young.  C. prunifera is also said to be somewhat cold-hardy.