That's a really insightful historical analysis. However, I don't think that quite addresses the point the author is trying to make. Perhaps I'm overstepping the mark slightly, but I think the author would claim that it doesn't matter if it takes another 100 years or a 1000 years more for democratic societies to form. What does matter (for the author) is that they would form, and that when they did, that story would be the history we have today.
However, I do think the points you make about the history are interesting, and perhaps an engrossing thought exercise is to contemplate how the world might look in the 21st century without the American Revolution taking place when it did. Apologies if I've misinterpreted your or the author's points.
Part of the entire idea of a democracy or republic is that government is only legitimate when it comes with the consent of the governed - and yet no one consented to the governance or laws made before they were born!
In political philosophy, this is not what it means to consent to be governed. Most social contract theorists would argue that by virtue of living within the society/state, you have implicitly consented to being governed. That is the nature of the social contract. As such, in being a member of that society, you consent not just to all laws being passed, but all laws previously passed. Further, this idea of an explicit consent doesn't make sense, eg. if someone wants to avoid being subject to a certain law, they cannot simply not 'consent' to it.
For a democracy to be legitimate in the sense that you describe it is a truism. According to these social contract theorists, the democracy by definition comes with the consent of the governed. Additionally, there are other methods of obtaining legitimacy, such as justified coercion and right to rule.
That is not to say that your overall point about Sunset Clauses is invalid, but I feel this section subtracts rather than adds to your reasoning. From my perspective, you have already offered suitable reasoning to support your view in the benefit section not to require a section on the philosophical sense.
I'd like to add that this is an interesting article and I'm interested to conduct some more research on some of these suggestions.
I think the point the author is trying to make is that even if America hadn't become democratic, another country would have soon after, and that country would have had the strong/knock-on effect you refer to.
Does taking the pill stop these people from being human? It seems like in an alternative interpretation could be that given William can master anything a human can do, then (assuming the others are human) he would able to do anything that the pills allow? Could be an interesting 'alternative universe' to consider. Captivating post!
In the first counter-examples you make the assumption that people who are young are persons, in the sense that they are worth moral consideration. Some would maintain that children are not people, and thus any action regarding them cannot be considered moral/immoral. In other words, their consent does not matter as they are not 'actors'. In that way Decius' claim that all actors must consent would still be true, as you are the only actor in that scenario. I'd be curious to read about any justification you would cite for the treatment of children as moral actors.
However, that said, I find your second example to be more convincing, but I'd be interested to know how the nature of the unconsciousness might affect your view. Would someone in a vegetative state also be considered as a moral actor in your view (and thus should be saved)?
Your point about it being difficult to leave society is one of the most common objections to social contract theory. However, you have misunderstood what implicit consent is. This article offers a clear explanation of what explicit and implicit consent are. I recommend reading it in full, but I'll quickly draw out the most relevant sections.
This is the form of contract that you spoke about as "consent" above.
This is what is meant by implicit consent. Implicit consent is different from the person disagreeing because they still take the action they would if they explicitly consented, from which it can be deducted that they do consent. By ordering the burger, it can be known that you consent to paying for it. If the waitress brought you the burger and you denied to pay, this would be ridiculous as you consented to pay when you ordered it. Does this make sense? To not consent would be to not order the burger in the first place.
There is also a third kind explored in the article, hypothetical consent, which might be worth a read. I do acknowledge your question on 'what people need to do so that people stop saying you consent' is difficult to answer, but it is one of the most central questions in social contract theory. As such, I don't have a single answer for you, but I hope this was able to clear up a little what 'implicit consent' actually means. If you'd like to discuss more on what this barrier of consent is, I'd be happy to discuss further.