My wife is only 5'7", so not tall by U.S./Norwegian standards.
When I was there, as long as I didn't do anything more than nod and say please and thank you, I was mistaken for a Norwegian.
I'm 6'2" so I was taller than most of the Norwegian men, though, there were a larger percentage of men taller than me than here in the Western U.S. (which I think is slightly taller than the Eastern U.S.). One of the men was my wife's uncle who was 6'9" and ran his own farm. I had the firmest handshake of anyone I've ever met.
We were at a viking ship museum in Oslo, in the gift shop when we overheard some Americans asking about the horned helmets and where they could buy one or at least borrow it for pictures. The elderly lady working in the gift shop calmly explained to them in perfect English that no self-respecting Viking would ever wear such a helmet, as the horns would help guide blows from above
into their head.
At that moment, I was rather embarassed to be an American.
Fortunately, my wife and I are were both wearing sensible shoes (tennis shoes are a dead give away for Americans) and dressier clothes (shirt with a collar, as t-shirts are give-aways for Americans and Brits) and my wife picked that moment to start a conversation in her perfect Norwegian with a lady standing near us.
I think we pulled it off.