Why did America suffer fewer casualties in World War 2 than many other countries?

In World War II, America suffered fewer casualties than many other countries (and other major combatants) for several reasons. The most important is that America did not enter the war until over two years had passed. Another reason is that American military leaders generally committed to tactics whereby as much territory could be gained with as little human cost as possible. This commitment entailed the assembly of massive firepower-support for all operations, which frequently led to success with lower casualties than would otherwise have been possible.