If one travels, one sooner or later needs to go to the loo, usually in a public-ish toilet (public-ish as sometimes it belongs to a cafe or a restaurant and is nominally provided for clients).
And one thing that differs the world over is the attitude to public-ish toilets - as seen by this post about the need to bring your own toilet paper in Chile.
In fact bringing your own toilet paper is generally a good idea anywhere, availability and quality can vary dramatically from location to location. So here's my summary:
Australia - almost always free. Ones in servos and airports are usually not to bad, the long drops in national parks can be smelly, and the roadside dunnies, especially in NSW, can be disgusting. Own paper, own hand sanitiser and a bottle of water to wash of any residue from the sanitiser a good idea.
Singapore - nowadays clean, functional and generally ok
France - can be sit downs, can be squatters. If it's not in a cafe or a restaurant can be disgusting. Own toilet paper, hand sanitiser etc a must, along with a ready supply of small change. Attended toilets are generally clean and pleasant.
Spain - surprisingly good. Countryside seems infested by underemployed middle aged women with a bleach fixation who look after servo toilets.
Netherlands - usually clean and efficient.
Germany - beware the nice trick of putting the toilet paper dispenser outside of the stalls - a bit of forethought can be required.
Morocco - small change is always required and the quality can vary from glistening to disgusting. Carry your own paper, hand sanitiser and a bottle of water. One of the oddest experiences I had was in a hotel where the attendant flushed the loo for you (and expected a tip)
Greece - again surprisingly good, but remember that the paper goes in the bin and not down the loo.
Turkey - varies from the glistening to disgusting but usually ok. Carry your own requisites and remember that paper goes in the bin, not down the loo. Also not all toilets flush - instead you fill that nice little green plastic watering can from the tap and use that to wash your residue away.
Thailand and Laos, much as Turkey, except that the paper can go down the loo. Be alert to the implications of cheap hotels that mention asian style toilets - this could simply be a squatter, or could involve that nice little watering can again ...
Malaysia - variable. In the cities can be clean and sparkling, but in the country rather more like Thailand or Laos. Small change and requisites generally a good idea.
United States - go to McDonald's (or indeed any other reasonable fast food restaurant)
UK - highly variable, rarely disgusting, but often not quite as clean as you'd expect. Public ones at main train stations are extortionate. Having some small change is usually a good idea, as increasing is following the US strategy of going to fast food restaurants to use the loo