"Brokers in Singapore told The Wall Street Journal that a tanker called the Skipper was the vessel seized off Venezuela early Wednesday. The tanker, formerly called the Adisa, had been sanctioned by the U.S. Treasury Department’s Office of Foreign Assets Control for carrying Iranian crude" [1].
[1] https://www.wsj.com/world/americas/u-s-seizes-oil-tanker-off...
Most Venezuelan oil is very heavy and sour and needs to be mixed with lighter oil to be refined and they need access to restricted chemicals for the process. As it was explained to me a few months ago Iran provides lighter oil, solvents and materials for the refining and they take the heavier oil to sell it in the black market.
Sanctions aside the tanker was there for the taking by any government. Spoofing location and flying a false flag are enough to justify boarding and seizure by any country since it's a stateless ship likely involved in illegal activities.
In short yes, USA does it because it can and there's legal justification for it beyond "Trump oil, Trump bad lel", but as usual HN devolves to a potato when world events touch USA politics.