Must ALL U.S. Allies Be Part of NATO?

There's a silly premise behind this:

...Russian President Vladimir Putin will advance until he meets steel. Until this week he met mush in, of all places, the United States government thanks to Republican Senator Rand Paul from Kentucky who used an arcane senate rule to block a vote on the accession of tiny Montenegro -- the former Yugoslav republic on the Adriatic between Albania and Croatia -- from joining NATO....--Michael Totten quoted at AOSHQ

The silly premise is this:  that all US allies in Europe should be part of NATO.  Is there a "right" to NATO membership?  A "right" to demanding US arms and armies for protection? 

Does Mr. Totten argue--just as foolishly--that there is a "right" to immigration to the USA?  What is the difference?  Hmmmmm??