No they can’t. If they buy certain Russian things the US will stop. Look at what happened when Turkey bought Russia’s air defense systems. They lost F-35s over it[1].

[1] https://www.defensenews.com/pentagon/2020/12/14/us-sanctions...

Vendor lock in. It’s hard to walk away from billions of dollars of hardware…

And just because the USA does buy and use Saudi oil, doesn’t mean American oil companies aren’t pumping it, shipping it or profiting from its sale. And it’s sold in US dollars