“But they are hardly the only reason or even the principal reason why the US has been involved in Ukraine, Georgia and most of the rest of the post-Soviet states since the 90s.”
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It’s about putting US and NATO (same difference) military bases up against the Russian border, akin to prospects we rejected being done against the US in 1962.
Not really, as there were no permanent non-local military installations in the new NATO states until recently, after Russia violated both the INF and Conventional Forces Europe treaties. Let alone nuclear weapons.
Russian forces are present in Cuba and Venezuela even now, by the way.