Despite your creative exegesis of Marshalls words, you still lack any statement by him to the effect Vattel supplies the rule of law on birth citizenship in the U.S.
It can be very difficult to persuade a person who believes they see something that the something isn't there. (Those ninja frogmen appear in post-crash photos and won't leave.) But let me approach this from a different angle.
In his dissent in U.S. v Wong Kim Ark, Chief Justice Fuller was urging that Vattel's natural born citizen rule (as opposed to the majority s common law rule) provide the decision in the case. Yet Fuller says nothing about John Marshall and The Venus. Now, if Marshall were saying what you claim for him, then Fuller absolutely blew a great opportunity to bolster his argument by showing his illustrious predecessor likewise cited to Vattel for the American rule on citizenship.
But Chief Justice Fuller knew Chief Justice Marshall didn't say that. You're merely seeing what's not there.