In Nordic countries North Europe is often understood as a synonym for Nordic countries, thus many Finns don't consider Estonia or the UK as "Northern European" for example.
Something I've noticed is that 'Northern Europe/North Europe' is one of the least defined regions, I've seen definitions ranging from just the Nordic countries, to them plus Britain and Ireland to those plus the Low countries to the latter including Germany.
What traits do Swedes and Norwegians have in common that Finns do not?

(I am curious.) And do not mention language. There were several mutually incomprehensible North Germanic dialects in Sweden and Norway.
With the exception of some minority populations, Norwegians, Swedes and Danes all speak dialects of a single language, just like Americans, Britons, Irish, Australians, Canadians, South Africans etc. all speak dialects of English; the only real linguistic differences I can think of is that the letter ash is written as Æ in all but Swedish, while the Swedes use Ä, however that aside, while there may be some issues with accents, Swedes, Danes and Norwegians (well, the majority atleast, the minority who insist on Nynorsk have more difficulties in writing) can all understand each others standard (and thus the majority form) language dialect; actually now that I think about it Scanidnavian (as in the language which the national languages are all dialects of, similar to Serbo-Croatian) is probably somewhere between the differences between the English dialects and the Iberian languages.
Aside from language they share common ancestry groups and they've generally been part of the same polity alot (Iceland and Norway have been part of Denmark and Sweden and then the Kalmar Union).
As I said though, similarities are not universal, there are different levels, and the Scandinavian identity is simply a sub-grouping of the Nordic identity, they're not exclusive.