When the US places financial sanctions on one country, it de facto sanctions many other countries as well — including many of its allies.
This is because not all countries and firms are interested in participating in the US sanctions-based foreign policy. Sanctions, after all, have become a favorite go-to strategy for American policymakers who seek to isolate or punish foreign states that don’t cooperate with US international policy goals.
In recent years, the US has been most active in imposing new sanctions on Russia and Iran, with many consequences for US allies who are still open to doing business with both of those countries.