However much of a threat Kaliningrad can pose to NATO, it can only ever have a temporary impact. Russia has no plausible means of long-term defense of the enclave beyond an offensive that would open a corridor through NATO territory. While Russian forces might enjoy temporary superiority in the Baltics and eastern Poland, NATO forces would undoubtedly concentrate on overrunning Kaliningrad as quickly as possible. NATO would also subject the enclave to consistent and overwhelming electronic and PGM attacks at the initiation of hostilities, hoping to destroy or disrupt any offensive capabilities before they could do the same to NATO.
Russian leverage is highest in peacetime. It will drop as ammunition is used up and nor replaced, as NATO inflicts losses on Russian weapons and infrastructure in Kaliningrad, and as NATO troop defeat the Russian defenders (three brigades, I believe, plus whatever paramilitary forces are available as light infantry) and take the exclave.
Preventing a Russian link up with Kaliningrad should Russia use force against NATO is why I want a robust defense of the Suwalki Gap.
And why I want a NATO offensive to defeat the Russian ground forces in Kaliningrad.
Apart from nukes, Russia is not a formidable military power except when faced with far weaker opposition.
And honestly, part of Russia's nuclear potential relies on believing that weaknesses in the rest of their military aren't present in their nuclear forces, too. We kind of have to assume that Russian nuclear weapons are a serious threat in case they are. And even in the worst case of Russia having only a fraction of their nuclear forces capable of launching would mean Russia could devastate Western cities.
But in the conventional sphere? Russia would lose a land war if confronted by real enemies willing to fight them.
UPDATE: On the nuclear factor:
Any American president faces the same basic dilemma. Russia is a country in decline, but it remains a potential threat to the United States and others because it is the one country with enough missiles and nuclear warheads to destroy the United States.
The nuclear-armed sick man of Europe which we don't want gobbling up weaker friends or propping up dictators and fomenting death and destruction; but which we don't want to fall apart and leave large pieces to be picked up by China, leave smaller pieces to become jihadi havens, or put lots of nuclear missiles, material, and know-how on the black market.
Can't live with them. Can't live without them.
UPDATE: More on Russia's reliance on nukes to make up for their weak conventional ability to stop a serious invasion.
America went through this early in the Cold War and we found out that a strategy of massive retaliation threatened against an invasion of the NATO West through West Germany was not credible against lower-level threats that threatened less than vital interests. Russia will find the same thing: that threatening mutual nuclear annihilation makes no sense when the stakes are small.
Good Lord, under what cloud of medically sanctioned marijuana is it really credible to threaten nuclear war in order to save Assad in Syria?