Mammuthus (mammoths) don't go extinct. After the last glacial retreat, mammoths manage to survive after the ice age.
10,000 years ago: Mammoths don't go extinct but most of them die apart from North America and the colder parts of Europe and Asia.
43 - 84 AD: Celtic Britons use mammoths to hold off Roman Invaders but Romans still conquer like they did in OTL.
200s - 700s: Mammoths are hunted to near extinction in most parts of Europe apart from Scandinavia.
790s - 1000s: Vikings use mammoths as war beasts which makes Vikings feared even more.
1492 - 1800s: Native Americans use mammoths to fight off Europeans.