If WW3 comes to pass, Americans likely won't be shielded. Since Russia lost 26 million citizens during WWII; at least one intellectual, with close ties to the Kremlin, has firmly stated that Russian will never again fight a war on Russian territory. If you do a search on "won't be fought on Russian soil", you'll learn of other journalists or Russian experts, who believe that Russia will bring the fight to the continental U.S. Here is one such statement by Russian experts currently working and living in the U.S. The Saker is a former Russian military analyst for the Swedish military (officer rank: Major).
A Russian Warning -- June 1, 2016 -- Vineyard of The Saker
If there is going to be a war with Russia, then the United States
will most certainly be destroyed, and most of us will end up dead.