Is there any visa requirement for US citizens entering Norway? How about the Neatherlands?
Both are Schengen countries, so US citizens need only their passport to enter as a tourist for up to 90 days. For other purposes or for longer a visa is needed.
At present there are restrictions due to covid, which are unrelated to visa issues.
When you begin planning a trip, it’s a good idea to go to https://travel.state.gov/content/travel.html to find out what documents and vaccines are required and if it’s safe to travel there.