I enjoyed reading the bio on Colonel Chamberlain. He was not only intellectually strong but an intuitive leader. And, yes, he should be lauded for ordering the bayonet church down the hill that shocked the Southern troops causing them to retreat in a disorderly fashion; and, so went the battle in Union favor. Isn't it amazing how the actions of just one man or woman can change the course of history.
Regarding your main point, your question. I believe the answer begins in a study of the founding fathers, not the battles and human events you mention. I do think your subject, your question's answer starts at the founding of the Nation. Many were Christian; and, some were deists, and they believed strongly in a God or a Divine Providence, an almighty creator, in a God but not in a religion in the case of deists. They were not only believers in God many were well studied in history, the classics and governments , and all were aware, knew especially the unacceptable rule of a king and a country, England. They not only were believers, they sensed a responsibility to their God or divine being to accomplish well what they did in the writing of the Constitution and the Bill of Rights. I do not think that their sense of responsibility, personal life preparation, extensive study and developed intellect were "luck". And, we could argue all day on whether we are 'blessed' by God in the creation and survival of this unique Nation. I do not think anyone, however, can make an informed argument against the fact that these men that not only did they feel a responsibility to God as a Christian or deist to draft those two documents, they were very inspired or influenced by God or Divine Providence in what the documents should say and not say and the compromises made.
From my knowledge of history before this Nation's founding and since, there has not been another government constitution or anything resembling the Bill of Rights written with such wisdom, practicality, unselfish content, truly written for the benefit, freedoms and protection of the people. One way or another we were blessed. Also remarkable the documents are devoid of theology or a state religion. Call it proof or blessed inspired by or whatever but it has been most pragmatic to survive some two centuries since finally ratified with the last needed signatures on September 17, 1787, an 11 years after the 13 colonies declared independence from the King and England. If not "blessed", it is most remarkable in the history of man to not only survive longer than any other living "constitution" today, but to be written by men, many infused in faith in God but to not include their beliefs in religion in the Constitution, even to protect the people from an establishment of a state religion.
Maybe the real question may be, is such an infusion, belief in God as a Christian or Divine Providence as a deist the meaning of "blessed"? In other words, did or did not Divine Providence or "God", bless this nation through these men directly or indirectly? Whatever happened, this Nation has endured and our Constitution and Bill of Rights have served this nation well in providing a basis of governance that endures and continues today. They did a pretty good job of it. It was more than "luck" any way you slice it – Their God was part of them. Well, that at least adds some discussion of the beginning of the United States and how God may have acted or at least inspired, influenced it all.
I regret I do not have time and energy to discuss the events you mention beyond the founding and what was God's role. I apologize but my reading sources for attribution for a basis of my discussion on the founding fathers escapes me. Isn't it interesting that not all were Christians, politically correct 'go to church' men. Thank you for the opportunity to the discuss this subject with you.
Regards, Peter
*Thomas Jefferson did not actually participate in the drafting but his influence was far reaching enough to affect those doing the drafting. There were no Jews, atheists, Muslims among the founders, those who drafted the Constitution and Bill of Rights; only Christians and some deists.