Indonesia is actually a pretty large an diverse country, but I haven't visited all corners, so I have no idea how much pronunciation of Bahasa Indonesia varies.
However, such differences are primarily differences in accent. Basic pronunciation is still the same. Sure Brits may say 'ah' where Americans might say 'ay', but they don't suddenly pronounce the 'gh' in 'enough' in a different way. Apart from some differences in idiom (pissed), they can understand each other perfectly. Rhotic versus non-rhotic is the only real big difference I'm aware of: some English speakers pronounce the 'r', some skip it.
> Rhotic versus non-rhotic is the only real big difference I'm aware of
There's always more out there than we're aware of. One famous difference is that in Australian english, the words can ("a can of tuna") and can ("I can do that") don't rhyme (I believe "can" is actually the wrong word in AE for "a can of tuna", but the example is just there to illustrate the word's meaning).
> such differences are primarily differences in accent
These obviously exist, but they're often so regular that they don't present much of an obstacle to communication. Vocabulary differences ("a tin of tuna" for "a can of tuna") and meaning differences (like the story where British politicians wanted a motion tabled immediately, because it was important, but American ones felt strongly that it shouldn't be tabled at all, because it was important) happen too.
Australian, British, and American english are nevertheless fairly close. How do you feel about Jamaican english (which is, in its vernacular, not mutually intelligible with the three I just mentioned)?
However, such differences are primarily differences in accent. Basic pronunciation is still the same. Sure Brits may say 'ah' where Americans might say 'ay', but they don't suddenly pronounce the 'gh' in 'enough' in a different way. Apart from some differences in idiom (pissed), they can understand each other perfectly. Rhotic versus non-rhotic is the only real big difference I'm aware of: some English speakers pronounce the 'r', some skip it.