USA & Canada Border the Most Undefended Border in the World 🇺🇸🇨🇦 The Slash - the Longest Treeless Zone 🌲 #usa #alaska #unitedstates #canada #states #49parallel #border #usborder #uscanadaborder #usborder #canadaborder #northamericanborders #uniquegeography #us #learn #map #maps #geography #history #viralfact #facts #fyp #geotok #historytok