Although this article is interesting and thought-provoking, your historical analysis is profoundly flawed. The United States is NOT the first constitutional democracy at scale: the English constitution pre-dates it, and was scaled outwards to form Great Britain and then the United Kingdom. England had a parliamentary republic in the mid-17th Century with an elected House of Commons and the House of Lords abolished; despite collapsing in 1660, this helped inform the authors of the American Revolution 130 years later. The 18th Century British constitutional monarchy was subordinate to ministerial responsibility, and from 1714 onwards all ministers had to be parliamentarians, predominantly from the elected House of Commons. Government policy was dictated by elected politicians, although the electoral process (in England, dating back to the 14th century) had become corrupted. The interesting thing about the American Revolution was that it was a civil war supported by reformers on both sides of the Atlantic: British reformers wanted to oppose George III’s attempts to regain the dominant hand in policy and reform elections, and the American Revolution enabled them to break his prestige. The Revolution help enable British reform, but did not inform it; the political principles were already centuries old. (Which is where the Revolution got its slogans from: e.g. “No taxation without representation” is a political principle dating back to 14th Century England.)
Across the 19th and 20th Centuries it was the British Empire and not the US that created democracies across the English-speaking world: Canada, Australia, New Zealand, India and the Caribbean owe their democratic constitutions to the UK, not the US, which is why they are Westminster-style parliamentary democracies. Similarly, constitutions in France, Germany and Japan are modelled on the Westminster system, not the American Constitution, due to post-war reconstruction influenced by Britain (e.g. although the US dominated the post-war occupation of Japan, American constitutional principles did not lend themselves to a re-made democratic Japan as well as their British counterparts, hence the latter were chosen.) If American democratic constitutionalism fails, there are other independent sources to uphold democratic government worldwide.