Looking at the rest...
Yellow cheese - we et Leicester...the "plastic" cheese isn't the colour, it's the way that Macca's cheese "melts" at relatively low temperatures that earned it's fast food name.
Twinkies - yes, they are ooccasionally available (always at Costco and the like), and are a bit over the top for most Aussies.
Starbucks - that's VERY old data...Aussies are flocking to the sweeter coffees full of fat and sugar these days...not the majority, but a mug of black with milk on the side (my preference) is fading quickly. Those of us who enjoy a macchiato are being outnumbered by the young...who instead of beer will have vodka lolly waters (even the blokes).
American bacon - again really old data...it's well and truly on the rise in eateries...I had breakfast at 11:30 (left the motel for a plane at 5:30), in the Blue Mountains, and it was "streaky" bacon.
PBandJ - I had them for school lunches back in the '70s. Jelly is "Jam", and could be strawberry, Raspberry, Blackberry, or Apricot back in the day (replete with skins and seeds)...now there's more. My kids used to make it occasionally. Peanut Butter and Honey is more common (we have real honey).
Sweet potato casserole - agreed. But there's occasionally sweet potato pie and pumpkin pie around the place..not common.
Grits - Polenta came to Australia from Europe, and you heve been able to buy it dry as meal for ever. Nan cooked it occasionally. for 20 years have been able to buy slabs of it cooked in the pasta section for slicing and BBQing.