The Russian NK-32/33 engines are very good as the Soviets were able to use the turbine exhaust for the fuel & oxygen for boost, instead of venting it. This makes the Russian engine 10+% more powerful than US designs. SpaceX engines don’t have the feature & are not as powerful.
How hard could it be for an American company to produce a knock-off of the Russian design?
While I don't doubt this for a second, the huge problem I see is the possibility of Russia delivering a few subtly sabotaged engines in a large delivery.
5 or 10% of all engines having a crucial bearing replaced with a lead alloy fake part that X-rays the same as the real thing and requires major disassembly to test otherwise, would set us back by years.
Not to mention the possibility of simply waiting until our engine supply is at a low point and then refusing to sell more.