I know that for a conventional war the US would protect the NATO members as we always have.
But the question of a nuclear war between Russia and the EU is a much tougher calculation.
There is no such thing as "conventional large-scale (or even "regional") war". And anyway, there is already nuclear dimension in the current conflict.
Next step is resume of nuclear testing and, hghly likely, it will happen this year.
See there you go with ancient history again.
"Those who do not learn history are doomed to repeat it.", as they say.
The current EU countries are not aggressive.
Of course they are aggressive. They hired Ukrainians and Baltics to attack Russians. Tomorrow they will go in battle by themselves. They just don't have another option.
We had to kick their asses to get them to boost military spending. I don't evaluate how much lives are worth. I evaluate their souls, you can look at a country and see their art, their standard of living, their cities' architecture, and their universities and see what kind of soul they have. When I look at Iran I see tunnels, missiles, nuclear weapons programs, ICBMs, killing peaceful protesters, hanging young wrestlers, threatening female soccer players, nothing but hate and violence.
It's not what you are looking by yourself. It's what media show you. When I, as a young soldier, started to study American culture, it was very specific view - poisons, chemical weapons, incendiarity weapons, nuclear weapons, biological weapons and their delivery systems, tortures, interrogations, covert operations, tactical and strategic planning, etc... And only later I understood that "real" Americans, Frenches and Japanese are not just "paper targets", they are human beings.
We don't take countries like Russia does.
Of course you do. Look at Hawai, Republic of Texas and others.
Look at Iraq. We gave Iraqis their freedom from Saddam and his insane and sadistic sons.
You just turned the country in chaos and killed much more Arabs than Saddam and all his relatives together.
That wasn't us, that was Israel.
It was US-lead coalition (Epstain Coalition). And you are responsible for it. Even if Trump decided that now Bibi makes all decisions - it's still Trump's decision.
Ok, lets leave well enough alone. No one wins a nuclear war.
We are going to win it. Even in your scenario with 90 mln killed, it's definitely not a Doomsday.