On which side would the US join the fight? Its movement towards Russia and away from NATO is accelerating dramatically, and it’s not clear where the trend will stop. Culturally, the US is increasingly at odds with scolds of liberal Europe and in tune with domineering Muscovite Russia.
If the US sided with Russia against Europe a big chunk of the US population would oppose that. (But even staying neutral and not supporting a NATO nation should one be attacked by Russia would be a bad outcome.)
