In the US a single PE+N wire feeds into the building. All building wiring is separated as in Europe. They are tied together in only one location, usually wherever the main switch is.
Just like Europe, really old installs in the US don't have ground (PE). Some are retrofitted with ground like my house in SF. One thing people should never do is connect neutral to ground at a secondary point. It can be tempting when you don't have access to run a ground wire but creates a serious potential for safety problems. The way to handle that is to install a GFCI (RCD) plug and put a sticker on it stating "No equipment ground" - the outlets actually come with those stickers for that purpose :)
As far as I know in European systems where the building has separate PE+N feeds they are still bonded together, it just happens at the transformer. I could be wrong about that though!
It could be different in US, but in modern European installations the PE and N bars are separate; older installations use common PEN; and even older ones don't even have PE. Each of the wiring schemes requires different approach and poses different hazards. There's no single recipe that would work on all of them.
My bottom line is: don't make arbitrary connections in the breaker box without proper knowledge and training; and don't give random electrical advice on the internet without knowledge of local codes.