Final Mission (Did I miss anything?)

[Raiken 10]

I wonder what I could have done differently because:

I captured all of Chernarussia, destroyed the chDKZ base and investigated the island where I find Lopotev which I did not manage to capture but who was killed every time (I tried). I never managed to get control of the USMC and am not sure whether that was actually supposed to happen. So I destroyed the Russian base which was the only thing left to me. Then in the final mission we are nuked. How could I have avoided this???