Generally speaking the word "societal" is only used when speaking of a society as whole, as in, "The American public is a societal melting pot of many cultures". The word "Social" can also be used to refer to the whole of a society, but is most commonly understood to refer to small groups with in a larger society, as in "New York City has a very divers social structure." The word, Social or societal, could be used in either of these instances but societal, feels better when used to refer to society as a whole.

The problem I see here, is not the proper usage of of the word societal, but has to do with a greater societal problem with the American culture. In the past, the American culture was one that encouraged people to strive for personal excellence at all levels. They had very high standards that people had to live up to in order to gain respect within the society. In other words, the bar of acceptability was placed very high and people had to reach up to reach it. Unfortunately, the modern American culture has lowered the bar of acceptability so low that you have to dig down to get to it, and anyone one that tries to raise that bar up is attacked as being 'Pretentious". The modern American culture abhors the idea that there should be a standard that a person must try to live up to and fights to keep any such standard from arising. We want a standard that anyone can reach, even without trying. Actually, in some social groups within the American culture, they actually pride themselves in their complete and utter inadequacy and incompetency. In these social groups, they consider the bar of acceptability to be one that encourages them to become the most useless, reprobate and disrespectful human being they can be. The unfortunate thing is that, I have observed that the trend of these social groups at striving for dis-excellence has permeated the American societal culture as a whole.

Even in the comments to this question we can clearly see those that overtly attack anyone that would try to strive for linguistic excellence. Their argument has not been that to use the word "Societal" is improper (if used in the proper context), but that the people using it are only trying to use it to pretend to be better then others (pretentious). This is a very typical and common response among this this modern American culture that encourages dis-excellence and attacks and tries to discourage anyone one that would dare to strive for excellence.

The fact is that "Societal" is a recognized word that has a proper usage. The idea that the word can only be used by a certain group of people (social sciences) and that anyone else who tries to use it is only being pretentious, is a farce that is only perpetuated by those that seek to promote dis-excellence and want to discourage any attempt at raising the societal bar of acceptability.