A few minutes on the U.S. CDC web site yielded the following round numbers for annual mortality in the United States from 2013, the most recent available data, in categories selected by me. (Some deaths will be in multiple categories.) This is out of about 2,500,000 deaths total.

War: 15

Complications of surgical or medical care: 2,800

Drowning: 3,400

HIV: 7,000

Firearms: 34,000

Suicide: 41,000

Motor Vehicles: 43,500

Drugs: 46,000

Diabetes: 76,000

Alcohol: 88,000

Smoking: 480,000

Cancers: 585,000

Off hand, speaking as a dilettante economist, I’d say if we want to make a real difference in saving lives, we should start by outlawing cigarettes. Then alcohol.