What If the US Invaded the Caribbean Islands?

What would be the benefits and what the drawbacks for the US of invading all the Caribbean island countries with the intention of seizing and selling off (or just taxing) the land and businesses there and taking the revenues? What's preventing them from doing this today? Where would it stop if they then took all of Central America and then Oceania and then kept going? If the US is the world's strongest military power (with diplomatic immunity from sanctions no matter what it does), how are they better off by not trying to grab more world from themselves by force?