Blavatsky never returned to the United States after leaving for India. But she did keep certain contacts there (see for example her correspondence with William Q. Judge http://www.blavatskyarchives.com/hpbwqjtab.html) and sent nice letters to the American Theosophical conventions, which were re-published over the years; some of her best explanations of what Theosophy is can be found therein:http://www.theosociety.org/pasadena/hpb-am/hpb-am1.htm
From the first letter, 1888, quite eloquent:
"I am confident that, when the real nature of Theosophy is understood, the prejudice against it, now so unfortunately prevalent, will die out. Theosophists are of necessity the friends of all movements in the world, whether intellectual or simply practical, for the amelioration of the condition of mankind. We are the friends of all those who fight against drunkenness, against cruelty to animals, against injustice to women, against corruption in society or in government, although we do not meddle in politics. We are the friends of those who exercise practical charity, who seek to lift a little of the tremendous weight of misery that is crushing down the poor. But, in our quality of Theosophists, we cannot engage in any one of these great works in particular. As individuals we may do so, but as Theosophists we have a larger, more important, and much more difficult work to do. (1)
People say that Theosophists should show what is in them, that "the tree is known by its fruit." Let them build dwellings for the poor, it is said, let them open "soup kitchens," etc., etc., and the world will believe that there is something in Theosophy. These good people forget that Theosophists, as such, are poor, and that the Founders themselves are poorer than any, and that one of them, at any rate, the humble writer of these lines, has no property of her own, and has to work hard for her daily bread whenever she finds time from her Theosophical duties. (2)
The function of Theosophists is to open men's hearts and understandings to charity, justice, and generosity, attributes which belong specifically to the human kingdom and are natural to man when he has developed the qualities of a human being. Theosophy teaches the animal-man to be a human-man; and when people have learnt to think and feel as truly human beings should feel and think, they will act humanely, and works of charity, justice, and generosity will be done spontaneously by all."
Image thanks to: http://www.flightcentre.com.au/travel-news/destinations/american-independence-day-key-destinations/
(1) Blavatsky did eventually give support to a charitable London school for girls, even delivering a rare public speech at the official opening event.
(2) Blavatsky had steady writing contracts for Russian periodicals, contributing semi-autobiographical mystical travel writings (which are probably some of her most underated writings -see her From the Caves and Jungles of Hindostan, The People of the Blue Mountains, The Durbar in Lahore)