The American constitutional system based on the separation of powers was modeled on a transitional stage in the evolution of democracy as experienced in 18th century England. With Kings struggling to retain power against insurgent parliamentary forces, a precarious imbalance of power existed which the Founding Fathers copied in America, but sought to stabilize by an ingenious though precarious system of checks and balances. When other countries imitated this plan — as in virtually all of Latin America and some countries in Africa, Asia, and the post-Soviet arena — they typically experienced break-downs followed by despotism. By contrast, in the United States, despite severe crises such as a major Civil War and the Depression, the system has survived until today, a truly exceptional experience that calls for explanations, as proposed here.
Meanwhile, all the other industrial democracies, on the basis of 19th century developments in the UK, have adopted a significantly different constitutional design based on an the accountability of Cabinet Government to Parliamentary controls that evolved in England half a century after the American Revolution. Although no constitutional plan can guarantee success for any country, the likelihood that parliamentary regimes will survive is far greater than the prospects for those based on the separation-of-powers. Even the best recipe can be spoiled by a bad cook, but all cooks are more likely to succeed following better rather than worse recipes.