If those victims would be primarily from western country, especially US, there would be almost immediate class action lawsuit against Boeing from families (US citizens seem more trigger-happy to fire lawsuits when feeling wronged, at least from my perspective).
But I guess Ethiopian/Indonesian cries for some sort of compensation/justice would have to go very viral in western media to force a corporation like Boeing into anything (since it is also a clear admission its purely their fault, which it seems to be).
Most countries don't have such a thing as class action, and even among the countries that have it, it's only commonly used in the one that invented the idea, and multi-national class action isn't really a thing. So I think you'd find that, far from "especially in the US," you should only expect a class action lawsuit like that for a flight that is either to or from (or both) a US airport.
With lots of of passengers on both flights being from lots of different countries, what they're getting instead is lots and lots and lots of individual lawsuits all being filed in different jurisdictions.
Which is, I'm guessing, likely to be more damaging to them in the long run.
MH370 was a multi-national class-action lawsuit filed in SC that was only dismissed because the circumstances of the disappearance were not clear and nothing to do with it being multi-national