Though native to North America - since the 16th-17th century, the cactus plant has spread throughout the world.
While I'm familiar with how cactus leaves are eaten in Mexican cuisine - I've never heard of dishes from other parts of the world that involve cactus leaves. A quick search on Wikipedia - which is always correct - says that cactus is commercially grown throughout North Africa. But I'm not familiar of any cactus leaf dishes. Are there any? Do cactus leaves appear in any other cusines?
I do believe you are correct about the prickly pear - however I've lived in Israel now for over 5 years, and for a country that has nicknamed the native born after the prickly pear (translation Sabra, a quick summary being thorny on the outside, sweet on the inside) - it actually doesn't appear much in Israel cooking.
The fruit is available and eaten, but basically as a stand alone and doesn't have too much prevalence in the overall food culture.