The fairly flat, circular part of the galaxy is referred to as the disk.
I hope this helps.
I can’t see what you need help with. Did you screenshot it?
The main reason is that the USA is in the Northern Hemisphere & Australia is in the Southern Hemisphere. It has all to do with the tilt of the earth as it revolves around the Sun. Summer happens in the hemisphere tilted towards the Sun, and winter happens in the hemisphere tilted away from the Sun.
Channel Tunnel, CN Tower, Empire State Building, Golden Gate Bridge, Itaipu Dam, North Sea Protection Works (Netherlands), Panama Canal. Hope this helps!