Also:

"In 2006 in the United States homicide was the second leading cause of death for infants. Homicide with a firearm was the second leading cause of persons between the ages of 10 and 24, the third leading cause of death for persons between ages 25 and 34 and the fourth leading cause of death for persons between ages 5 and 9 or between ages 35 and 44. For persons between ages 45 and 64 homicide with a firearm was the seventh leading cause of death. Homicide with a firearm or by any means was not among the top ten causes of death for persons aged 65 or older whereas there were at least two forms of homicide among the top ten causes of death for all persons under age 44. (See 10 Leading Causes of Injury Death by Age Group for details.)"

How many of those homicides are drug related?

Police themselves say that about two thirds of all the homicides in the USA are related to the War on Drugs: suppliers, dealers, consumers or battles of any of these with police.

Taking them at face value (which I admit would need to be checked), it would mean that the "underlying" murder rate of the USA is one third of what it shows as in current statistics. This would be well within the range of Western Europe and East Asia. Where drug-related murders are rare, so their own rate wouldn't move down so much in the absence of their respective versions of the War on Drugs.