They keystone of US global power is its ability to have the back yard locked down. Undisputed control of the Caribbean region ensures that the USA can operate as it pleases in the entire Western hemisphere. This shake up in Venezuela during a time of US government paralysis is exactly what the Russians and Chinese were hoping for when they endeavored to exacerbate the divisions in American society during the 2016 elections.
What we are seeing play out now is the best chance since the Cold War for an Old World power to regain a foothold in the Americas to challenge US dominance over the hemisphere and therefore the world at large.
Watch the Chinese, they are being quiet. Russian bluster is to be expected but Russia becomes Beijing's puppet more and more as time passes.