In 2014, the US mistakenly shipped(Opens in a new window) a neutered, non-explosive training version of a Hellfire air-to-ground missile to Cuba, instead of America. It had been in Spain for a training exercise, moved around between European cities for a while as it prepared for the journey home -- but then, it was somehow mistakenly loaded onto a cargo flight headed directly from Paris to Havana, reportedly along with a bunch of non-military cargo. The US has asked the Cuban government to return it, but the Cubans are being clear on the issue of givesies backsies: They just don't do it.
How bad is this, really? Well, the missile has no explosive payload or working propulsion system, but it's a real Hellfire missile in just about every other way. Its design could be extremely helpful to engineers in any number of countries looking to build better missiles, or design better countermeasures to American ones. That sounds pretty bad, doesn't it? Cuba could sell the dummy missile to Russia, China -- anybody!
But, let's look at how the Hellfire has been doing over the past several years. Most trivially, the US Army lost a dummy Hellfire(Opens in a new window) over New York just last September, simply because it slipped off an aircraft in mid-flight it seems, but they later got it back. Worse, there's good reason to suspect that China and other cyber-powers might already have blueprints for the Hellfire and more, thanks to the still-vague scope(Opens in a new window) of several highly successful(Opens in a new window) military cyber-attacks on the US and its allies. And of course, the US sells thousands upon thousands of working Hellfires to "close" military "allies" like Iraq,(Opens in a new window) Saudi Arabia(Opens in a new window), and Turkey(Opens in a new window).
By far the worst recent example of the Hellfire being compromised, however, is the fall of Iraq's Mosul to forces from ISIS (or Daesh, if you prefer), which led to the entire compliment(Opens in a new window) of US munitions falling into the hands of terrorists. Remember that ISIS doesn't have much in the way of air power to actually fire these sorts of missiles, so we can only assume that the cash-hungry organization at least tried to sell them off. Pretty much the only non-Shia US rival government I can't imagine secretly getting in on that action would be Russia, given its totally overriding organizational hatred of Islamists -- though even that might not be enough to sour the prospect of getting one over on the old U. S. of A.
Compared with these and other Hellfire-related breaches or risks, it seems hard to justify being all that upset about a dummy missile ending up in Cuba. It's certainly embarrassing, and doubly so because Cuba is refusing to return the thing, but anyone who might credibly buy it from Cuba, and to whom Cuba might credibly sell it, could easily have been a potential Hellfire customer for a long time now through overtures to even less-ethical actors.
And, not to sound like too much of an idealist, but Cuba is just on the brink of seeing what it might be able to gain through diplomacy with the US, rather than strife. It's not the Cold War anymore, and the younger Castro doesn't see Cuba's continued existence as mutually exclusive with America's. It makes less sense for Cuba to tick the US off now than at any time since the island nation didn't actually attack(Opens in a new window) the USS Maine at the turn of the last century.
You always have to take threats like this seriously, and shore up leaks wherever you find them. However, as far as the proliferation of US war tech is concerned, terrifyingly, this is just a drop in the bucket.
