You need a way to change language on your webpage. Many, if not most visitors from UAE cannot read Arabic, and most AE websites will in my experience default to English. But justwatch has seemingly no way to change from Arabic when visiting from UAE.
If I go to justwaych.com/us, it changes to English, but now I suppose I am browsing US availability. Again, this isn't written anywhere, so I don't know if what I'm browsing or searching is available.
You can change language and country independently from each other. Just click on the Account settings in the top left/right corner (depending on locale) and change it there.
When not signed in, the button just says "Sign In", which is not something anyone would look for a language change option - doubly so if the "Sign In" in is in a foreign language. There is plenty of space to add a globe icon or something like it directly on the page there.
Letterboxd uses their API. I track my watchlist on Letterboxd and can filter movies available to stream in my subscriber services thanks to their use of the JustWatch API.
There's a trend in my country (Italy) where old movies are being remastered in HD but not published on Blu-ray. Instead, they're only made available on one out of a half dozen or so streaming services. JustWatch helps me immensely to spot new releases like that!