In a really informative episode of Things You Might Not Know, host Tom Scott handed the screen over to deaf vlogger Rikki Poynter, who explained about different forms of sign language used in different countries and cultures, even if the same spoken language is used in more than one country.
For example, Poynter explained that even though the United States, the United Kingdom, Canada and Australia speak regional forms of English, the sign language used in each country is very different. While the deaf community in the U.S. communicates with American Sign Language (ASL), the U.K. employs British Sign Language (BSL), Australia uses Auslan and although much of Canada uses ASL, Quebec specifically uses Langue des signes du Québec (LSQ). Poynter also makes note of several internationally understood symbols.
Of course, just like you may see similarities in spoken languages, you will see them in various sign languages. …Naturally, people wonder, “Why can’t we have just one sign language? Wouldn’t it be easier that way?” If that happened, that would make things boring. Yes, it would probably make things easier, but we already have different spoken languages, so why not have different sign languages?