On one of our Alaska trips we carried a second spare, unmounted. Of course non of the spares were needed.
Chances of getting severe tire damage are greater in the lower 48 where many interstates are worse than anything you will encounter in Canada or Alaska.
Boat: 32' 1996 Albin 32+2, single Cummins 315hp
40+ night per year overnighter
2007 Alpenlite 34RLR
2006 Chevy 3500 LT, CC,LB 6.6L Diesel
Ham Radio: VP9KL, IRLP node 7995