Probably a failed constitutional convention in the late 18th century.
However, I'm really not sure if the term "balkanization" would be appropriate to describe a united states that split into many smaller states and republics. If I understand my European history adequately, the Balkans were and are split into numerous self-identified and at times mutually hostile nationalities separated by ethnicity, language, and religion. The term also implies disfunction and warfare.
If the initial USA dissolved into a number of fully independent republics in the late 1700's or early 1800's, they would all be English-speaking, contain a British-descended citizenry, be dominated by Protestant Christianity in one form or another, and share common values described in the 1776 Declaration of Independence. These sucessor states may well have conflicts as they each complete with each other to settle the west, but there was an earlier history of alliance and confederation. The biggest risk of a balkanized US is that the weakened and smaller states would be unable to retain independence in the long term when faced by expansionist European empires. If they did remain independent, I suspect that a "balkanized" USA would look more like the modern EU rather than the balkans of the 19th and 20th century.
However, I'm really not sure if the term "balkanization" would be appropriate to describe a united states that split into many smaller states and republics. If I understand my European history adequately, the Balkans were and are split into numerous self-identified and at times mutually hostile nationalities separated by ethnicity, language, and religion. The term also implies disfunction and warfare.
If the initial USA dissolved into a number of fully independent republics in the late 1700's or early 1800's, they would all be English-speaking, contain a British-descended citizenry, be dominated by Protestant Christianity in one form or another, and share common values described in the 1776 Declaration of Independence. These sucessor states may well have conflicts as they each complete with each other to settle the west, but there was an earlier history of alliance and confederation. The biggest risk of a balkanized US is that the weakened and smaller states would be unable to retain independence in the long term when faced by expansionist European empires. If they did remain independent, I suspect that a "balkanized" USA would look more like the modern EU rather than the balkans of the 19th and 20th century.