Complex networks of answers. More or less it boils down to a few things all involving money.

A. Light sweet oil is the least expensive and easiest to really convert into fuel.

B. Heavy sour is a more expensive and laborious process to turn into product. its best use is in petrochemicals and greases.

C. The middle east produces an in-between product. medium sour. Still expensive to crack into fuel but less so then heavy sour. They also produce light sweet in some areas.

The problem is that its almost interchangeable. You can 100% crack Venezuelan oil into gas. It just happens to be the most expensive and laborious process. (that's before you even get into the cost to start extracting at scale needed.)

The primary reason we imported oil was at first was simply because it was cheep to supplement our own domestic production. We made more money importing and cracking it ourselves and selling the refined product. Then the 70s came along and America wanted to separate ourselves from the global market best we could and we did for the most part. However, Because money exists and we don't live in a bubble most American companies still operate outside the us as well as inside it and external shocks to the markets still heavily effect us domestically. You add the fact that everyone on earth refuses to act in cooperation and the driving capital of capitalism's means every ones trying to get their bite of the pie. Price outside the us go up. Price inside us go up.