I.e. significantly longer than the US
I couldn't help but following your link after you said that, since it's one of those, "I knew Norway had a lot of coast, but THAT much?!" moments for me. I did want to point out that the numbers even at the link you shared are a bit incongruous, since they seem to vary quite a bit from source to source based on how they define a coast or shore (e.g. do they include freshwater or inland bodies of water? if they're measuring the actual coast (as opposed to the boundary of jurisdictional waters), are they measuring to a particular depth of tidal water, or are they measuring the shore as it's represented on a map? are overseas territories included in the country's total? ). For instance, here are some official numbers, most of which were pulled from the Wikipedia article you linked (I also grabbed numbers from other sources I've linked):
25,148 km (World Factbook) or 53,199 km (World Resources Institute) or 125,225 km (Statistics Norway)
19,924 km (World Factbook) or 133,312 km (World Resources Institute) or 153,646 km (NOAA)
All of which is to say, while I can't say with any certainty which has the longer coastline (not that it matters), it's indisputable that the overall point you were driving at--that Norway has a LOT of coast (particularly given its size) and that it impacts things in all sorts of ways that most of us may be unaware of--is both correct and inherently fascinating. Thanks for sharing the info!
In case you're curious about the massive differences in the numbers...
The World Resource Institute's dataset was designed to be used for comparisons between countries. They talk at that link about the difficulty in producing useful numbers and in comparing numbers from different sources. To get around most of the issues they identified, they used a vectorization of the coastlines at a constant resolution (to ensure that no country benefitted from having a more detailed mapping than other countries) and didn't include overseas territories. As such, theirs are useful approximations for the purpose of comparisons and are relatively accurate as far as these sorts of measurements go, but for coastlines with lots of nooks and crannies (e.g. Norway's), their approximations may have a greater degree of error than they would for locations with simpler coastlines.
NOAA and Statistics Norway are, I believe, both official organizations, but I wasn't able to find much about the methodology that either used. NOAA mentions that it includes outlying territories, so that immediately inflates their numbers a bit. They also include the shorelines of the Great Lakes, which makes some sense given that they are boundary waters between the US and Canada, but some people may question their inclusion. Either way, it's probably safe to say that both NOAA and Statistics Norway are working with highly detailed maps when making their measurements, so they're likely to be closer to the true numbers than the World Resource Institute's, though it's difficult to compare them without adjusting for differences in methodology.
As for the CIA World Factbook, they don't list their methodology in a place I could find, but it's pretty clear from their numbers for landlocked countries that they're not including inland bodies of water. Given how much lower their numbers are than everyone else's, I'd wager they were calculated at a low resolution, or else they may simply measure at a set distance from the shore, effectively decreasing the resolution of their measurements significantly.
At the end of the day, it looks like the US' coastline may be slightly longer, but the country also benefits from being significantly larger. Back at the first Wikipedia page you linked, Norway is listed by the World Resource Institute as having 175 meters of coast per km^2 of land area, while the US only has about 15 m/km^2, which just goes to show how much crazier the Norwegian coast is than the coast around most of the US.