All three are excellent weapons, but I would go with the Garand, simply because it is semi-automatic. I think that would give the American soldier a significant advantage in the kind of combat a soldier would face.
A semi-automatic weapon requires minimum effort to fire several rounds, which can be a drawback if one is conserving ammo, but can definitely make a difference when things are moving quickly, as they often are in battle. The single-action rifle, such as the Enfield, requires the shooter to operate the bolt between shots and that not only takes time, it can spoil the aim.
Those of us who got acquainted with the M-16 may recall having been advised to move the safety directly to full automatic in a firefight. The ability to squeeze off a burst of three rounds can make a difference.
If the soldiers have time to acquire the target, aim and get it done with one round, the differences between the rifles are less significant. All three are accurate rifles, but usually multiple rounds help assure a hit.
Good question. I've been trying to think of a good ground-combat scenario, but was leaning more toward battle tanks or artillery.
In my case I have a small problem of being left-eye dominant. That makes it more difficult to fire a standard rifle or a camera, which are designed for right-eyed, right-handed people. So I would favor the semi-automatic rifle because it is easier for me to concentrate on my aim.
Oddly enough I am right-handed. Normally left-eyed people are left-handed as well. It makes pistol shooting more difficult for me being cross-dominant, but knowing about it helps me compensate.
I am not a terrible shot, but it is difficult for me to be a really good marksman. A semi-automatic or automatic weapon can help make up for that.