The United States taxes each barrel of imported oil at a flat rate.

 The statement you've made isn't a question, but rather a point about US policy regarding the taxation of imported oil. I'll turn this into a question to provide an answer: "How does the United States tax each barrel of imported oil?"

As of my knowledge cutoff in 2023, the United States generally does not tax each barrel of imported oil at a flat rate. Oil imports are typically subject to customs duties based on their value rather than a specific tax per barrel. However, this can vary depending on the trade agreements between the United States and the country of origin, as well as current U.S. legislation which could change over time.

In the past, the United States has imposed various forms of taxation on oil imports including tariffs, but these are not a consistent flat rate tax per barrel. When tariffs are imposed, they could be either a percentage of the value (ad valorem) or a fixed monetary amount per physical unit, but these tariffs would be subject to change depending on economic and political factors.

It's also important to note that the taxation and duties on oil can be influenced by geopolitical events, changes in domestic energy policy, and international trade agreements. Any specific tariff or tax would be established by legislation or executive action, and thus one would need to refer to the most current information for the exact details of such a tax.