Biden has just said that Nato won't do a thing about it.
“It’s one thing if it’s a minor incursion, and then we end up having a fight about what to do and not do,” he said. “But if they actually do what they’re capable of doing with the force amassed on the border, it is going to be a disaster for Russia.”
When he was first asked about the Ukraine crisis, Mr Biden said: "He (Mr Putin) has never seen sanctions like the ones I've promised if he moves (into Ukraine)."
So the USA will do nothing if it's minor, and sanctions (like not buying gas) if they invade properly.
Europe needs Russian gas to get through the winter. There is enough LNG in the world to supply Europe, but there aren't enough ships to get it here or ports for them to unload. That's ignoring the financial cost.
This leaves the EU to "fight" alone, in the dark as rolling power cuts sweep across Europe.