I get the impression that this is more a matter of public indoctrination than any realistic proposal to draft people.
Conscripts don't make very good troops, frankly. Modern warfare doesn't really need them. Certainly not such a mechanised military as the US, or, for that matter, most NATO countries.
But it seems to suit the purposes of some to maintain a state of threat.
America is undefeatable. It is essentially, uninvadable. This is due, in part to its military but mostly because its geography, the diversity of its government, the numbers of beligerent civilians.
In all honesty, if some foreigh state took over control of Washington DC, how many Americans would instantly salute their new overloards and follow whatever?
I don't want to get into any discussion on the purposes of this nonsense. Partly because I doubt many Americans are able, at this time, to seriously look at any evidence, without feeling conspired against, but mainly because this isn't really the sort of forum in which that discussion is relevant.
However, as a non-American, I suggest that it is really just an excercise in enforced enrollment in patrotism. It can do little or no har, but could create problems if you refuse.
In the mean time, have a look at this:
http://www.draftregistration.us/