Anyone can be an enemy in principle. It is about hedging your bets. Joining an alliance with the most powerful military in the world seemed like a smart choice to many. But it was far from an obvious choice.
Norway and Sweden began developing nuclear weapons after WWII for self defense, and many in Norway wanted us to stay neutral as had long been our policy in wars. Especially since many did not see Russia as our enemy.
It was a political issue fought hard. It was controversial enough that our largest party, the labour party fractured into two parties because of it. Half the party opposed NATO membership and formed a new party, that still exists.
In fact Norway specifically sought a compromise to make people accept this choice. E.g. American military bases on Norwegian soil was banned, something former Soviet states like the Baltics specifically wanted because they explicitly feared a Soviet invasion. We also banned placement of nuclear missiles aimed at Russia.
Norway also engaged in a lot of cooperation with the USSR during the cold war in part to show that we did not view them as enemies. In fact this was a frequent friction with the US which of course wanted to pain the USSR as the evil empire.
It is not like we didn't know that the USSR was a dictatorship, but there was always hope for reforms. And small countries don't see the world the same way as large powerful ones. When you are small, you don't have the luxury of making enemies left and right at your own leisure. Great powers always have to be placated.
You don't know when they will invade you as part of their games. Germany did not have anything specifically against Norway, but we happened to be strategically important for their war. Just like Britain didn't have anything specifically against Norway when they attacked us during the Napoleonic wars, stole our ships and embargoed the country, probably killing more people than the Germans ever did due to hunger. People were eating bark of the treest to try to survive.
It is not always clear who will invade you next. One tends to focus on the last perpetrator, which is why many prior to German invasion actually feared British invasion more.
