I believe the ingredients were always different due to Australia's "Allowed Substances" list and local ingredients availability. Similar to the controversy over "Pink Slime" for their beef patties never being an issue here, because the substance was already banned.

USA (according to https://www.mcdonalds.com/us/en-us/product/chicken-mcnuggets... ) :

Ingredients: White Boneless Chicken, Water, Vegetable Oil (canola Oil, Corn Oil, Soybean Oil, Hydrogenated Soybean Oil), Enriched Flour (bleached Wheat Flour, Niacin, Reduced Iron, Thiamine Mononitrate, Riboflavin, Folic Acid), Bleached Wheat Flour, Yellow Corn Flour, Vegetable Starch (modified Corn, Wheat, Rice, Pea, Corn), Salt, Leavening (baking Soda, Sodium Aluminum Phosphate, Sodium Acid Pyrophosphate, Calcium Lactate, Monocalcium Phosphate), Spices, Yeast Extract, Lemon Juice Solids, Dextrose, Natural Flavors.

Australia (according to the PDFs here https://mcdonalds.com.au/maccas-food/nutrition ):

Ingredients: Chicken, Water, Flour (Wheat, Corn), Canola Oil, Starch (1420, 1422, Corn, Wheat, Tapioca), Mineral Salts (450, 500, 451, 341, 327), Salt, Spices (Celery, White Pepper, Black Pepper), Sunflower Oil, Dextrose.

> What are McNuggets made of in the US?

It was Pink Slime for awhile. "Real Chicken" is the continuing strategy to claw back from the PR nightmare.

https://www.eatthis.com/mcdonalds-debunks-rumor-about-mcnugg...

https://colors-newyork.com/who-uses-pink-slime-list-2020/