Culture has a huge impact on what people find funny, and residents of different countries, even those that speak the same language and have a lot of cultural similarities such as the United States and Great Britain, may use humor in different ways. For example, British humor is typically seen as more dry, sardonic and ironic than American humor, which may be more slapsticky and physical. Some research has shown that people of all cultures may broadly find situations with some sort of incongruity that is eventually resolved to be funny, which is known as the incongruity-resolution theory, but the specifics of what each culture finds to be incongruous may be so different that it's impossible to get universal cross-cultural laughs out of the same joke.
Things such as cultural norms relating to manners may have a great impact on what people from one country find funny that others can't relate to. Going back to the United States vs. Great Britain example, Americans do tend to "get" irony in the way British people use it, but they may feel uncomfortable being that deadpan themselves, feeling the need to add a caveat such as "just kidding" that Brits may feel would ruin the joke. But even within a single country, differences such as age, gender, class and education level are going to impact what people find funny.