The thing is, the US's local agents, the upper class comparador elite that ran the country for over 150 years, and were subservient to first London banking interests and then fully under US control after the 1890's, are just too weak.
So without local agents, you need an army to invade. The other countries in the region have already voiced their displeasure with a US military invasion. And the pro-American elements of the army are outnumbered by the revolutionaries installed by Chavez. So, if/when Maduro is overthrown, the counter coup will be viscous, bloody and you'll probably have an even more anti-US government.
You see the collapse of the rule of law and criminal gangs around Venezuela which is paralyzing the police. However, Maduro isn't a guy who has killed tens of thousands in a purge of his opponents. He doesn't like conflict and killing. But what's destructive is he is naive and utterly clueless about economics, currency management, and international trade.