Like Hitler's Germany, the current Russians are practicing a little bit of geo-political jujitsu.

"The US has something called the Monroe Doctrine, which says we're not going to allow any foreign activity anywhere in The Americas, and that doesn't just mean North America, that means South America too, that's ... a massive zone of control."  .........we've taken over places to defend American minorities before"

We understand the idea of  "sphere of influence."
"Buffer states" and "zones of control" are not a thing of the past.
We don't think they are old-fashioned ideas when it comes to our sphere of influence.

"When Adolph Hitler and the Germans (before the Second World War broke out) were trying to state that there were territories outside of Germany that should be handed to Germany;  the excuse that they used was that there were Germans in these areas...and they were being persecuted by their neighbours" (that was the problem with taking pieces of Imperial Germany and making them into new countries after WW1)

"So when we propose NATO Membership for  Ukraine, the Russians just have to sit back and take that?"

From Common Sense with Dan Carlin  podcast  22 March 2014 (at the 5-12 minute mark)

[my note: Also, think about the 1916 Mexican Punitive Expedition led by General Pershing into Texas  to protect US citizens living in Texas, which at the time belonged to Mexico]