The issue is that the sovereignty of nation states is a somewhat nonsensical idea that has little to no solid philosophical backing. Nations aren’t living things and shouldn’t have rights in the same way people have. They are imaginary constructs, and the consequences of this are inevitable debates over what is or is not a nation. But there is no clear dividing line or definition—and in this ambiguity, powerful nations are free to recognize or ignore nations as they choose.

If you support the US action, you can claim that the Houthis are not a sovereign nation, the action was at the invitation of the legitimate government of this region against an terrorist organization, and was entirely legal and justified.

If you oppose the action, you claim that Houthis are a group of freedom fighters who have established a new separate nation that should be recognized, and this action was an illegal violation of that newfound sovereignty.

Neither can be said to be completely correct or incorrect because there is no solid basis for this idea of sovereignty.