And their size puts them in a different class. If a foreign entity has effective powers that make it similar in some ways to a foreign state, it makes sense to treat it as such.
Ok so sanction and fine their ass until they start behaving. If we can sanction north korea for having an ideology we don't like, surely brazil can sanction meta's ass for trying to blatantly meddle in another state's affairs. Bar every employee from traveling there. Freeze any assets. Use diplomacy to pressure the US to press charges. Make them come to heel for chrissake