Hi, is this possible for American mountain lions and African lions to mate and breed ?
Yes. Mountain Lion (Puma concolor) are native to the Rocky Mountains of North America but they have been introduced to some parts of Africa where they continue to interbreed with wild African Lions.

Mating between male mountain lion and female African lion can occur in several locations including forests, savanna grasslands and scrubland. The gestation period lasts around 70 days and cubs are born weighing just over two kilograms. As with many other big cats it is not clear what the impact of climate change or habitat loss will be on their populations in the future. However, with adequate prey and suitable habitats remaining they may still be able to thrive in certain areas.