It is very interesting. With the advent of fracking the US is oil independent, which correlates well with the loss of interest in oil rich countries post 2010. So why the new push to secure Venezuela? It seems they need cheap oil for something else.

Perhaps they are scared that if all the available oil is held in foreign hands it would be too easy for them to dethrone the Petro dollar. So if oil is selling for less than $40 (making shale not viable) and everyone able to provide it at thay low price won't sell for dollars anymore, suddenly the dollar loses value. However, if there is at least one source selling for dollars that changes.