"Even though cultures differ, people are basically the same."
This is a statement that depends a lot on what you mean with basically. I think people are pretty much the same all around the world but and they definitely could end up being almost the same if they was raised in exactly the same way and had the exact same possibilities in life.
If the basic characteristics are those you have when you're new-borned then I think it's obvious that they are almost the same, some things are of course genetic but I believe that the main part depends on your way of living.
It's not only the culture that matters but also the religion and the type of country you live in. These two naturally affects culture a lot and the culture affects them so there are no sharp limit between them.
An example from the book is the Australians, whose culture is rather close to the English, but there are few Englishmen who would have liked the loneliness in the big country Australia, and even fewer Australians, (I think), would feel comfortable in the crowded England.
Another example in the book that is more about religion and culture is the Japanese soldier who walked with the girls in Malaya when they got the stolen poultry from Joe. The soldier is abused by his captain and he finds it so humiliating that he looses his will to live. When he's infected by the fever he doesn't fight it and he dies. This is a mentality that is or maybe was very common in Japan. A person from the west would never feel so bad about loosing his face as a man from Japan.
The differences between cultures can be something that maybe some of the persons would like to change if they got the possibilities but it has never occurred to them to do so because they are used to the way it is. In the book this is found amongst the Malayan women that has to work on the fields, look after the kids and sleep on the floor.
I don't think that they would want to be repressed by...