Countries where lecture duration does not exceed one hour Most (probably all) universities attribute to each subject a fixed number of credits, which in turn are [most of the time] related to the time spent in classes. 

In Brazil, the majority of courses are worth 60 credits and lectures are 120 minutes long. During my undergrad (physics) I've watched several lectures from all over the world to help me study, many of them from the US, India and the UK. I've noticed that the lectures in the US and UK were rarely longer than 85-90 minutes, while in India they had most of the time the same duration as in Brazil (120 minutes). I felt that teachers in the US/UK covered less subject in their lectures, but at the same time it seemed as if they had covered exactly what could have given you a hard time studying on your own: intricate details of a proof, obscure references, hints to particular exercises, etc. In Brazil/India it just looked as if they were reading the book and explaining each and every little detail. The result was that, even though the 85 minute lecture covered specifically less than the 120 minute one, I had the impression that I learned more from it, and that it [obviously] made me feel less tired. 

I've taken several courses in physics and mathematics and, from my experience, I simply cannot stay focused for more than ~75 minutes in a lecture. I'm therefore wondering how does it work in countries all over the world. Studies like this one show that an even shorter lecture might be as effective as a longer one, and this layman review points out that people can only focus for 15 minutes in a row. This suggests that the optimal length of a lecture should not exceed one hour (perhaps much less), with breaks such that students can assimilate what's being taught. Is there a country where lecture time approaches such patterns, or where other strategies regarding lecture length optimization are employed?
Well in the UK we usually have 50 minute lectures of which we might have 2-3 per week on each subject. The evidence from educational research that I have read is that you can't stay focused listening for more than 20 minutes in a lecture so even in a 50 minute lecture it is good practice to break it up with something a bit different in the middle.