While broadly true, other countries regulators need to be active and keep the American regulators in check. The entire episode with FAA and Boeing 737-MAX make

While broadly true, other countries regulators need to be active and keep the American regulators in check. The entire episode with FAA and Boeing 737-MAX makes it clear that while Ethiopian regulator can not do airworthiness certification of such a complex plane they can definitely ground the fleet faster than FAA wanted to do. It is unlikely that FAA would have grounded the fleet until all other major bodies had done so and put it under a lot of pressure to also do so.