Forces within the international market have always controlled where the oil flows to (best market price). International demand and the price of oil per barrel have always controlled the amount of oil that flows. The United States of America does not, nor ever will extert any influence on either except in the extremely unlikely even it overnight abandons oil in favour of some other fuel.

The direction of oil supplies, again generally dictated by the market. If you are responsible for husbanding the natural resources of any country you tend to sell to whoever will give you the best price for it.

The international currency used throughout the oil industry is and always has been US Dollars. Historically the Oil & Gas Industry is an "American" Industry, all major technological break-throughs and innovations related to down-hole and reservoir technology have been American. The US holds the vast majority of patents relating to Oil & Gas exploration and production activities. You cannot move anywhere in this industry without bumping into them.

Areas of the world where for political reasons this expertise is not brought to bear are those with the lowest operating efficiency - Iran, Iraq (although this will change now that Saddam has gone), Russia (This too is changing).