Sure, the mutual-defense guarantee can be a moderating force, or it can be a ticket to rapid escalation (case in point WW1) and, potentially therefore, nuclear war.

The fact that the Cold War ended peacefully, and with the USSR‘s dissolution to boot, is one of history’s great miracles. With the world’s return to its default multi-polar state, we really shouldn’t press our luck.

Give Russia and China their spheres of influence while we protect our own. The tail risk of nuclear war just isn’t worth whatever gains Neocons promise. After all, how did their Iraqi and Afghan experiments in democracy turn out?

Russia already has its sphere of influence, but it is rapidly shrinking because aligning with Russia offers neither peace nor prosperity nor anything else of value. Politically, economically, scientifically, and culturally, it is a dead end. Russia is not the first country to slip into irrelevance and struggle to accept the loss of its influence, and no amount of temper tantrums has ever changed that for anyone.

The UK, France, Belgium, Portugal, Spain, Italy, Turkey, Mongolia, and many others were vast empires at some point in history. They have all had to adopt a self-image that reflects their true political, cultural, and economic weight in the present world. Russian ambitions are too detached from reality, given that they account for only a percentage or two of global GDP and population, and are in a downward trend.

I don't disagree about Russia's prospects. China, too, is facing a demographic collapse it will take generations to mend. But the nuclear arsenal of both countries makes this irrelevant for policy now.