Even If india Iran russia belarus china will go all against NATO still NATO are stronger NATO got numbers.
If there is such a war then its nothing other than world war 3.
But things aren't that serious as you described and the only reason why Russia is having the upper hand is because many European countries still need the oil and gas from Russia to satisfy their oil requirements.
Things are kinda serious, when Ukraine shoots missiles into Poland (of Nato), and then tries to blame it on Russia, and then sends destructive drones into Russia and destroys airbases. Russia has had her fill of Ukraine, and the US is thinking twice about what their next move will be.