As usual, let's keep it short. China might be negotiating a military training facility in Cuba. If the deal will be struck this poses a great threat to the US. At first glance, one could think about the close proximity to the continental US but this is the smaller of the problems. If the US will start a campaign to undermine the whole endeavor then China will use this to show the world the double standards that the US presents. They will most certainly say that the US can have bases wherever it wants to protect its interests, so China can also do the same and as it happens its interests lay in Cuba.