To Americans...

[D-Dave]

Well, "not prosecuted" may be not perfectly correct but as you had the link handy I did not have, this is what I meant:

For four months the Peers Panel interviewed 398 witnesses, ranging from General Koster to the GIs of Charlie Company.  Over 20,000 pages of testimony were taken.  The Peers Report criticized the actions of both officers and enlisted men.  The report recommended action against dozens of men for rape, murder, or participation in the cover-up.

and

The Army's Criminal Investigation Division continued its separate investigation.  Most of the enlisted men who committed war crimes were no longer members of the military, and thus immune from prosecution by court-martial.
A 1955 Supreme Court decision, Toth vs Quarles, held that military courts cannot try former members of the armed services "no matter how intimate the connection between the offense and the concerns of military discipline."  Decisions were made to prosecute a total of twenty-five officers and enlisted men, including General Koster, Colonel Oran Henderson, Captain Medina.  In the end, however, only few  would be tried and only one, William Calley, would be found guilty

So it should have been more like "not enough prosecuted".

PS: BTW, thanks for the link, great resource for freshing up knowledge.