Are there any communities in America or Israel where women cover their hair before marriage? Do Satmar women cover their hair before marriage?
Sefardic women have a custom of covering when praying. See Yabia Omer,Yalkut Yosef or Halacha Berurah 2:19, where he says to be strict and cover when mentioning God's name, learning the Bible, saying blessings, bircat hamazon, or praying. In any case he brings that widespread practice is that single girls don't cover her hair.
It is not true that there aren't communities where this is done, rather most people are just ignorant to the fact that there are. These communities are not only found in Israel but other places as well. What happens is that often times, they keep to themselves, and people assume that the young single girls are married when they see them in public so they just don't know. The married women wear a double head covering just like men in many fervently orthodox communities do. This is the radid, the traditional Jewish (think Biblical) veil. This is still done in Yemen and in recently founded Yemenite diasporic communities including in NYC and in its suburbs. Since people tend to get tunnel vision, they don't notice that these girls don't have wedding rings on.
The Magein Avraham in siman 75 s.k. 3 has an interesting aproach to the subject. In order to mantain that the Shulchan Aruch does not contradict itself and to maintain the Rambam's opinion in light of a seemingly contradictory Gemara, he asserts that the pruas rosh that is assur for a single girl does not simply mean uncovered, but rather means let lose.
And there are communities that are very strict that single girls not walk with lose hair. Most hassidic communities keep girls hair in ponies. In some Israeli communities, old time Meah Shaarim comes to mind, the girls keep their hair in braids.
These minhagim are all built off the Magen Avraham and his understanding of Pruas Rosh by single girls. So in that sense, many people are stringent on this, even today. But even the Magen Avraham points out this is only a Rabbinic degree of tznius, not biblical.
Recently in Israel there are stories of a cult that does not exist in the United States. The information I've found about the cut can be read here: