Russia's [active] military is actually on par, give or take, with Turkey (not including strategic weapons). They have a ton of older hardware mothballed but still could be brought into operation quite quickly so if they did go on a rapid offensive (which is highly unlikely) most likely their meat grinder would steam roll a lot of Europe before a response could be mounted but highly unlikely to be able to sustain the logistics to win out in the longer run - Western nations would burn a lot of their high end hardware, with a lot of what would have been easily avoided early losses with better preparedness, stalling the advance due to a mixture of poor preparedness and complacency/hubris.
Ultimately it doesn't really achieve much for Russia - even victory would be hugely costly for what they could hold onto, wiping out any real gains, without the ability to actually hold all the territory they'd overrun (and likely leave them fairly weakened, vulnerable if China or the US, etc. decided to move against them).
EDIT: Something that concerns Russia more than our nuclear weapons even is our ability to wage war half-way across the globe - part of the reason they got involved with Syria was to improve their capabilities there and something they'd struggle with immensely with any assault on Europe - a smaller but more advanced and hard hitting force that can outmanoeuvre them strategically is a big threat so it saddens me to see how increasingly it is undervalued and reduced in this country.
People forget that major sticking point is the morale and ability to take huge losses while thinking you're fighting for a right cause. Russia will NOT invade western Europe at least as it is now. Russia does not need to be more powerful than whole nato combined to do this. All they need to do is sell the war to their population, which would allow ability to take huge losses (exactly what they are doing). Create a rift in west/east europe societies so the help would be minimal (exactly what they are doing). And there you go.
Again, given how Hungary, Poland is turning back on western values, will you or an American be conscripted happily without huge backlash to defend Poland? All they have to do is have enough power to send back couple thousand western NATO soldiers back in quick succession and possibly force a conscription to knock out any major wind.
Also given US performance with covid PPE in Europe... If current trend sticks I don't think we should rely on them too much either to come running in high water. Unless Ivans are going to start crossing over the channel.
Don't forget France in WW2, what a population that has no desire to fight can achieve.
On top of it all, Russian millitary is designed ultimately to combat America rather than anything else. That is why they are so heavily invested in their AA systems and hunter submarines for aircraft carriers.
I see the western world collapsing to smaller and smaller time-scales. This administration, Next administration. This quarter, second quarter etc. Russia under putin is playing a game decades ahead and it really worries me. We need to kick out a stool under putin before its too late. It has to be done by changing russian population minds - not anything else will work.
Finally why would Russia do this? Its not for land, its a culmination point of years of propaganda. Such what Brexit vote was. The writing is on the wall everywhere but people keep ignoring it.
