As far as the second part...well, it's like this. California is not a separate country, YET (even though it seems like it to us 'whites'). At some point though, the rest of the country may feel that way, and might be disinclined to sacrifice their children and tax dollars to defend it. At that point perhaps CA will sue to secede and be its own country, or perhaps become part of another country (some "Mexican-Americans" believe that this is a wonderful idea, and you can guess which country they would like to tag up with; fun stuff here: Reconquista Now! ).
In any event, the notion of a unified country with a common set of values will cease to exist. Oh, it might still be titularly unified, but that will be a joke. The ethnic differences will be stunning. Will all these nice people get together "for the common defense"? Nah. Look around you. Didja see lines around the block to join the Army on Sept. 12th? But that's what happened on Dec. 8th, 1941. Millions volunteered. It took weeks for the backlogs to be cleared. So we're already there in some ways. Ultimately this will lead to a more vulnerable country. Actually, it already has.
Forty years ago Mohammed Atta and his gang couldn't have walked around loose. People would have been instantaneously suspicious - even here in SJC, at least back then. Cops would have stopped them: whatcha doin here, furriner? But since virtually anyone can walk our streets now, and we are legally enjoined from impeding them based on any criteria at all, we are now vulnerable. The Japanese had to come in aircraft launched from carriers; these days the guys walk right in and set up operations. That's the future!
I don't expect the draft to make a comeback no matter what, for just those reasons. The "American people" may be too ethnically different in 30 years to ever expect that people from Iowa would team up with people from NYC or SFO and go out to fight. The US Armed forces will remain what it has become, a mercenary army controlled by a central government, rather than the citizen armies of the past, which were mainly state militias, activated for federal service in time of war. That is the reason I asked you about the military: to gauge your perceived willingness to identify as a part of a larger whole. Obviously, you don't. You segment the world into competing ethnicities. No surprise there. Everyone does!
Undoubtedly, there are those who will chime in and say, "but its always been this way in the US!". But that was when we had severe pressures to assimilate. With the numbers coming now, and the enormous cultural differences, that pressure has evaporated. And, as you said, no one knows what will happen.