I'd just use a Trident or a land-based ICBM (dial-a-yield set to max) to show them up close and personal *WHY* they don't want to tangle with us.
Remember, the US is the only power that has ever willingly, deliberately, nuked civilians; and we firebombed both Germany and Japan, too. Not that I'm particularly glad of that: but if the camel-humpers want to thump their chests, they should remember that we've "been there; done that; got the T-shirt" before most of them were even born.
And the result? Germany and Japan now make our automobiles...
But if you're squeamish, let's aim at their sole refinery first; or else some important military installation exclusive of a population center.
Cheers!
They have built many of their nuclear sites UNDER cities or highly populated neighborhoods, with that deterent in mind.
We are too gentle to attack and remove the threat, even if it will result in MILLIONS killed later.