Cannabis is legal for medicinal purposes in 29 states, with CBD (limited THC content) legal in 17. It's recreationally legal in 9 states, as well as DC. That leaves only four states with no approval.
In 2018, a number of states will be voting to legalize either recreational or medicinal marijuana. If trends continue, soon half the country will allow recreational and only a few (likely the same four as of now) will be against it completely, if that.
Canada (fellow G7 participant, and America's neighbor) will be legalizing it federally this year.