'Spoonfuls' doesn't help with the the impression that Vegemite needs to be portioned correctly. I would guess, most Americans are put off my Vegemite because their first notion is to grab a spoonful and shove it in their mouths with nothing else as they would with peanut butter. Of course it doesn't help thst, my guess from experience, is that most Australians would encourage the action while trying to hold back their laughter.
Disclosure: I am an American, I live in Australia, I like my Vegemite thin and my peanut butter thick :-)