A troop is a group of soldiers. Troops could be either the individual soldiers within the troop or a group of more than one troop. Troops when used to refer to individual soldiers within a troop may be an abbreviation of trooper(s)
CNN might say; American troops came under fire (meaning a group) or 3 British troops were killed today or a British troop was injured. I suppose the context helps to identify wkether it is singular or plural.
If you 'Google' troop, troops, you will find this subject widely discussed. Heres one to get you started
The Grammarphobia Blog: On "troop" and "troops"