You cannot compare Israel and America when it comes to army duty. Israel is surrounded by many enemies and is in constant danger, whereas USA starts wars accross the globe, 'cause USA puts her nose in matters that are none of her business. Israel needs all the (wo)men they can enlist in the IDF, due to terror and constant threats. USA does not need that many soldiers.
UN human rights office 'deeply disturbed' by Libya death sentences (Reuters)
from the article: IDF: Nearly 28% of Israeli males avoided conscription in 2007