1. Alaska is the most sparsely populated state in the nation by far. It has almost no military value. It is freezing cold, and mostly pristine wilderness.
2. The Russians don't want Alaska. Why would they? They already have plenty of land, especially land like Alaska. It's called SIBERIA.
3. Why would the Russians waste the element of surprise, the strategic advantage associated with a first strike, seizing land as worthless as Alaska? They might as well formally declare war and give us a 7 day warning. In other words, "not bother" with a preemptive strike in the first place.
4. Alaska isn't part of the continental United States. Even IF Russia did a blitzkreig/first strike and managed to take over the entire state, they still wouldn't have a beach-head from which to conquer the United States. They'd have hundreds of miles of sparsely populated Canada to trudge through before they got close to ANYTHING of value in North America. Their supply lines would be a general's cold sweat nightmare.
...and yet, the Mainstream Media is worked up into a frenzy, pushing propaganda that these close fly-bys are a HUGE deal.