Do you mean "bus stations outside the UK" or "bus stations in the Netherlands/ Germany/ Switzerland" (which are apparently the only countries outside the UK, since they are the only ones that we get compared to)?
I have no idea whether there are any other countries with public transport as the only ones ever discussed on the Forum are the Netherlands/ Germany/ Switzerland - presumably France/ Spain/ Italy/ USA etc don't have public transport, so we can't use them as benchmarks? Or is it that there are just three countries where they do have perfect public transport and we can only ever compare ourselves to them?
There are of course many other countries that have bus stations at rail stations even if the rail station is far from the town centre. Many if not most of the people reading this thread may not read the "Buses and Coaches" section so for the benefit of those people, the countries mentioned are often discussed there as they are widely recognised as having particularly good public transport.
As for bus stations... it really depends on the market. Some towns/ cities require them, some don't. Some have such big city centres that they have had several over the years, some large places only have a "coach" station. This kind of "one size fits all" policy doesn't help.
You're talking about the British scenario there, but that reminds me to point out that bus stations next to rail stations outside the UK very often don't have separate buildings. They may be fully integrated into the station building or be an array of bus stops outside the station so may not be thought of as "bus stations" in the British sense.