We are from the northern region, but are not accustomed to the cold at all.
「私達は北国出身ですが寒さには全く慣れません。」は英語で「We are from the north, but are not used to the cold at all.」という表現が良いと思います。
私たちーWe
北国出身ーFrom the north・Resident of the northern country/region/territories
寒さーColdness・Cold
全くーCompletely・Entirely
慣れるーTo get used to・To grow accustomed to 慣れませんーTo be unable to grow accustomed to・To not get used to
アメリカ合衆国 
