I would agree that there wasn't a specific turning point in the American Civil War.
There is an interesting book, published in 1960, called Why the North Won the Civil War (edited by David Donald). The title is a misnomer, it really should be Why the South Lost the Civil War. This book is a collection of five essays by historians looking at various aspects of the Civil War: economic, military, diplomatic, social, and political.
In the economic essay, the Union victory is attributed to both the greater Northern economy and to the misuse of the one economic resource the South did have (the King Cotton scheme).
The military essay points out deficiencies in both Union and Confederate strategies. These often resulted from the fact that most of the senior generals on both sides (as well as Jefferson Davis) were West Point graduates and had been taught tactics and strategy by Dennis Mahan. Mahan (the father of Alfred Thayer Mahan) was an admirer of a book written by one of Napoleon's generals, Baron Antoine Henri Jomini. The problems with Jomini were that technology had changed warfare since the Napoleonic wars and that Jomini had a flawed understanding of Napoleon's strategy and grand tactics. It wasn't until Grant and Sherman disgarded Jominian strategy that a Northern military victory became inevitable.
The diplomatic essay shows how the Union, primarily Lincoln and Seward, were able to persuade Britain and France from recognizing the Confederacy, even as a de facto government.
The author of the social essay offers the intriguing thesis that an excess of Southern democracy killed the Confederacy. From soldiers in the ranks to Davis himself, too much emphasis was placed on individual freedom and not enough on military discipline.
The political essay suggested the deficiencies of Davis as a civil and military leader turned the balance. It has been claimed, many times, that if Lincoln and Davis had switched places, the Confederacy would have had a much better chance of gaining its independence. It also brings out the point that the South suffered from the lack of a second political party to force its leadership into competence.
I recommend this book as one of the clearer, yet shorter, discussions on various aspects of the American Civil War. I should note that a basic knowledge of the war and its leading personalities is necessary to full appreciate the book. For instance, someone unfamiliar with the Erlanger Loan will not understand the economic essay.