Sorry if this may have been addressed, and for the record, I disagree with Russia's invasion of Ukraine, their propaganda, violation of free speech by media and their indiscriminate attacks on civilians.
I read a story recently about Ukraine's application to join NATO, basically putting a NATO country on the border with Russia. I'm wondering what the US would do if Mexico became an ally with Russia? NATO was formed to be mutual defense relationship with fellow members, in response to communism (in large part). The Warsaw Pact, which was Russia's NATO, was formed in the 1950's for the same reason, but it ended in 1991. You wonder why NATO is still relevant after Russia ended its mutual defense alliances.
My history is not as clear, but my recollection is that when Russia put missiles in Cuba, we tried to invade Cuba. And Russia only put missiles there AFTER we put missiles in Italy and Turkey, close enough for missile attack.
Technically Russia already has a couple NATO countries on its border, Latvia and another small one. They are small. The biggest border on western Russia is Ukraine (and Belarus). What’s the difference when a Chinese or Russian warship or military plane cruises the Pacific too close to our territorial waters. Or what if Mexico let Russia put a missile defense system in Juarez?
Again, I still disagree with Russia’s invasion, their propaganda and shelling of civilians, but I think the motives are a little more complicated than simply Russian expansion.
Just wanted thoughts from those who likely know more and have a better understanding of history.