Every country has internationally assigned call letter prefixes. But whether there is a requirement to use them on the air is a different issue.
In Ecuador when I owned stations, I once wanted to use the call letters as the station identifier because doing so would be unique among commercial stations; I was told I could not do that and I had to pick a name to use.
In Argentina, when I was licensing some music scheduling software, the vendor wanted "call letters" for the contract. Nobody in the building knew them. We called the government licensing bureau, and were told "we can look it up... call back tomorrow or the next day and we can find it." A few old, traditional stations there use their calls, but together with a name, like "LR3 Radio Belgrano" or the like.
Canada and Mexico, sort of emulating the pioneer US stations, use calls. Both require them in legal identification. But most newer stations use a name or slogan most of the time. Only heritage stations like KDKA and KFI and WOR use calls exclusively.
But technically every nation gives every station calls, but whether they are used varies by nation and by station.
