American Lion

Panthera leo atrox
Is an extinct lion endemic to North and South America and was the biggest lion ever to have lived. It became extinct after humans arrived in the America's. Lion bones have been found in the trash heaps of Paleolithic American Indians, suggesting human predation may have contributed to its extinction.
American lions likely preyed on deer, horses, North American camels, North American tapirs and American bison. They were the same species as the extant African and Asian Lions, though I imagine the idea of reintroducing lions to North America is not a popular one.