Vegemite and marmite are Australian spreads made from brewer's yeast. It's a big thing in Australia, but isn't such a big deal in the United States. In fact, I don't think more Americans would be used to the taste. It's extremely salty and strong, but when paired with the right foods it can be very satiating. It's as if the Australians are so tough that even their food is over seasoned to demonstrate their tongue's resolve.
Pasta is like rice in that you can throw anything in there and it might be good. I always keep a couple of boxes of pasta around because it's so simple and filling. 99 cents a box for three to four meals? Yes please! If you're sick of throwing dollar store ragu in your pasta, or if you're super lame, butter, then vegemite would work.