Don't generalize.
If one goes to one of these countries, one feels like going west. Otherwise, it's less and less.
So when Americans speak about Europe, it's safe to assume that they might refer to these countries.
Rock bands will always have a hard time to tell Bucharest from Budapest.
Similarly I'd suggest the point at which grape production for wine tails off would signify the start of Northern Europe. Wine grapes are grown in England, but I wouldn't call England a big wine producing country. Similarly, the Netherlands has some wine production but I wouldn't class them as a major wine producer and as such part of Northern Europe. North of Dusseldorf or Hannover? Arguably Northern Europe. South of Dresden? Probably Central Europe.
I completely appreciate this is made on no scientific basis whatsoever and I'm probably completely wrong, but if you visit Spain, southern France, Italy, Greece and Western Turkey you'll see remarkable cultural and ethnic differences and similarities between them and Austria, Poland, central and southern Germany and in turn Northern Germany, the Netherlands, northern France and the UK.
TL;DR - Europe's a mess. We can't even really all agree on what it is.
Greece, south of Romania, could also be included in the western countries.