I thought that Master of Sport in the Soviet Union and now in Russia corresponded to a rating of 2400+, but I didn't realize it's really 2450+ FIDE! Yikes.
A friend of mine some years ago, when training with GM Yudasin (who was brought up in the Leningrad school), was a strong expert (and would eventually make NM). He told me that Yudasin said to him something like "You are close to American master, but for Russian master...no no no, LOOOONG way to go!"
Following international tournaments I notice that there are LOTS of 2400, 2500+ players from Russia without FIDE titles that are basically strong IM or even GM strength. Incredible.
So in Russia, "NM" is generally superior to the general "IM" title? Wow, those guys are harsh. Ultimately though an individual shouldn't ask the federations for how "masterly" they are -- that's up to him or her to decide. The only problem is that for some countries, some players will be as strong or stronger than USCF NM's, yet won't be enjoying the same free membership.
Maybe chess.com is just too lazy to consider other NM's, I don't know.
Basically, yes. Then goes the Grandmaster of Russia title (2600+ ELO), which is more prestigious than GM. The ultimate title is "Honorary master of sports". To obtain it, one has to earn at least 150 points. To give you a sense of how hard it is, winning the World Chess Championship awards 75 points, European Chess Championship - 35 and the Russian Chess Championship - a meager 10 points, etc. I have recently completed the requirements, but haven't applied yet...