Several years ago my spouse was US Permanent Resident. She did not
need visa to visit Canada or Mexico; the US has (had?) agreements with
Canada and Mexico that US PR did not need visa for either country
(transiting the mutual border). I presume US - Canada have mutual
agreement that Canada Landed Immigrant does not need visa for US (when
arriving from Canada).

Call US consulate in Canada or try to visit website for current rules.