Sorry Garry, but you are not understanding the way most of the European countries see their own defense.
I appreciate you are giving a European perspective on this, but I suggest that NATO is America.
If the US didn't want NATO then it would not exist.
Any number of European countries could decide to withdraw from NATO and it would make no difference at all, but if the US withdrew NATO would stop being what it is... an instrument to pressure the Soviet Union and now Russia.
While the US sees the NATO as an instrument to try to have more countries involved in the military support of their political goals, most of the European countries seen the NATO only as an instrument to assure their own defense. Europe follows the US but in a minimum degree in most of the cases.
I suspect the US sees NATO as a way of turning europeans against Russia to stop any integration of Russia with europe.
It is not just Russia that threatens the hegemony of the US over the whole world... Europe with Russia or Europe with China or indeed Russia with China or just a lot of developed countries (ie BRICSA).... all have to be kept in the US camp or fighting each other.
India or China or Russia or many other countries could become powerful... and serious rivals to the US... the best way to keep them down is to keep them fighting amongst themselves and preventing relations with the rest of the west.
I'm sure that Russia is able to see how the US are trying to raise the tensions between Europe and Russia. And I'm sure that Russia understands how this Treaty affects not to the defense of the US in its own territory. To break this Treaty only would make that many European countries feel more endangered, raise their defense budgets, in most of the cases to buy American military equipment. Also would open the door to many more new nuclear weapons in Europe looking at Russia.
Instead of having to destroy London or Brussels or Paris with a TOPOL ICBM being able to do it with a cheap land based 5,000km range cruise missile would make things much cheaper for Russia.
Having to build a new integrated air defence network will cost NATO so much they will likely bankrupt themselves.
Today Russia can hit every geographical point of Europe with land, sea and air based nuclear weapons. The inverse case is not a reality, and it shows the attitude of most of the European countries toward Russia. The alone effect for Russia about to break this Treaty would be to allow, to impulse, the inverse situation becoming real.
Only by using the limited in number ICBMs can they hit any part of Europe with nuclear weapons from land based systems... Having IRBMs will overwhelm any ABM system the US introduces into europe and also having ground based cruise missiles will further expand their capability and ensure MAD.
Obviously to break this Treaty is the wrong direction for Russia, and I'm pretty sure Russia will not do it. In fact it is something that the US would like, and even can promote.
The US will not care really, except that there will be more ICBM warheads going to their shores in a future WWIII.
I suspect they would prefer Putin tear up the INF treaty than the New START as anaemic and pathetic as the latter is.
Russia has some concrete concerns, but I'm sure they will find the right way to deal with them.
Russia hasn't got many effective buttons they can push to piss off the Americans, but New Start and the INF treaty are two of the easiest and most obvious.
More importantly Russian technology has moved to the point where nuclear weapons on IRBMs in no longer critical to their effectiveness either.