Mountain Lion US keyboard layout .. bug? British layout when selected US keyboard When I change my input source to US Keyboard and I want to press this key: ` I get some British key.

My keyboard is this one: 



And it behaves like this one:



I changed my keyboard layout like described in this: stackexchange post but there is nothing changed. When I press the ` key I get that symbol as on British keyboard.

In result it looks like this:
I think your keyboard has been modified and is non-standard.  If for some reason you want what is printed on the keys to match up with what is typed, you could make a custom keyboard layout using

http://scripts.sil.org/ukelele