I sincerely doubt organizations like the KKK would all just flock to Dominica after this siege, nor do I think it would gather all the various white nationalist groups under a single island that could easily be watched. That's fictitious and wishful thinking at best, and a dangerous attempt to justify allowing a nearly guaranteed genocide to play out at worst.

The USSR may have been collapsing, but they also never had active actions by the US to act as a scapegoat for a new military campaign. It'd be backing a wounded animal into a corner and expecting it not to lash out in some form. And it can't be carried out by an organization the US denounces, and then receive its marching orders and send its profits to the US. Not even the most blindly patriotic of citizens would have that wool pulled over their eyes, let alone the more critical eyes of foreign powers or domestic cynics.

And then you must ask, for a country who hasn't done anything Anti-Western nor Anti-American, what's there to gain in letting a bunch of racist gunmen take it over? The United States, for what little credit I'll give it, wasn't dumb enough to try an occupation of another carribean country Grenada during its intervention into its affairs. Because there's nothing to be gained from going into these countries, annexing them, subjugating their populations to what could amount to slave labor and internment camps ((Turning the island into a strip mine would not get support from the people. And you can't just tell them tough shit and to get over it, without resulting to extreme measures like Stalin's regime did.)) But there is something to be gained from stepping back, and letting the country you don't need to take over flourish or fall on its own.

Mainly you save a lot more money and hard knocks from freedom fighters and guerrilla fighters, and you get to let islands continue giving you things such as their agricultural production or areas for financial and tourist activities to take place. And without the crippling sanctions being placed on you, like what happened with Russia and why its in perpetual economic downturns even with Putin at the wheel.