Our conscription laws are "All-Volunteer Army."
A basic Soldier today recieves more training then a Ranger did in World War II.
Obviously we are much, much more high tech. We lose less men due to technology. We don't need to send 100 boys to die when we can just launch a missle at it to get the job done.
Much better inteligence. We can use satelites or Predators (Unmanned Aerial Vehicle) to take a look at it rather then rely solely on recon teams.
Platoons/Squads seperated by miles today are in communication with each other to carry out battle plans. In World War II, that wasn't always possible due to radio equipment not having been around for that long.