I was looking at the US Sttae Department travel website yesterday, and it said the Norway and Switzerland were part of the Schengen area.
That's what I said. They're Schengen (so no immigration (passport) check when entering from another Schengen country) but not EU so officially, Customs inspection of your goods (but in reality, very, very rarely unless you go in the "something to declare" lane).
For further clarity, when you fly to a Schengen country via another Schengen, you clear Immigration at the connecting airport. But Customs is always at the final airport. At EU airports, there will generally be three lanes - red "something to declare, "green" nothing to declare, and blue "intra-EU travel exempt." Checked baggage tags from within the EU have a green stripe along the edge that helps make it obvious. From our experience at Stockholm, the red "something to declare" lane was actually the door into the Customs office while the green and blue lanes were combined as the "walk on by the office" corridor. Note also that "something to declare" means you believe you owe Customs duty. You do not need to make a declaration if what you have is covered by your exemptions.