Depending on the type of oil and the refinery availability it's not that simple. Not all sources of oil can go to all refineries.

Also, there's the bigger geopolitical problems that creates. If the US knocks over the global energy supply and then retreats and abandons our trading partners, the knock-on effects would be even worse.

A large part of the reason WWII existed was the breakdown of international trade during the Great Depression. Countries without domestic supplies of their own were forced to grab territory instead of peacefully trading for what they needed.

Why would they sell it for less when they could sell it for more?

We’re witnessing “American exceptionalism” transform from a brash claim to a whiny demand in real time.

The type of oil that the US produces (light and sweet) can't be handled by US refineries which need (heavy sours). Why we are still a major importer of oil.

I don’t think it is. If we can then also ensure the US stops meddling in international affairs, we can all be happy!

That's what Canadian oil is for. The USA gets it at a discount price.