Russia is far weaker than us, but they are fully capable of massively expanding beyond their current state (7.1% GDP currently on their war machine, no total population mobilization), and they can take it all the way through nuclear war if they are threatened to the point where this becomes an existential threat to them.
Your reasoning is typical for people that are insulated.
Let's hope there are enough rational minds left to where this does not become personal for us.
Then let us make it clear to them that this is not and existential threat to them.
Perhaps we do that by scaring the beJesus out of them, hurting them in some horrible horrible way and making sure they know more is waiting. And we are willing.