The story needs some help, it's very vague and confusing at times. Who is nuking the US? Is it Iran? If so then how does that make this WW3? Not to mention there's little to no chance their archaic nuclear missiles would get past the advanced ABM installations that the US has. If it is Russian ICBMs, then that would make a lot more sense, but then that begs the question, why? Why after all these years of peace between NATO and Russia would they risk MAD just to stop the US from invading Iran?
Story aside the level of detail in some scenes is fantastic, like how the heat wave from the nuke hits before the shock wave. Many big budget films miss that detail and have both hit simultaneously. (Although that does depend on how far you are from ground zero)