::some of whom saw their rights as being safer under the Crown than in an independent American republic 
 ::It still have the same problem  under the Crown, if it is to mean inside the British empire (no matter who the head of state is), is fine. However, if it means "inside a monarchy", it is original research. Since this article is about monarchism, the reader could easily make the wrong interpretation. In other words, you can't see an example of monarchism here, as a source that said "under the crown" probably used it as a synonym for the whole country/system (personification of the state as you call it). Also, "some" appears to be a weasel word.    

 *Republicans were seen as being generally of American origin, having thus been taught to admire republican government as the best in the world and to ridicule monarchism,[19] "a few individuals, who unfortunately, are led by those, whose hostility to the British constitution is such, that they would sacrifice any and every thing to pull it down, in order that they might build up a Republic on its ruins." 
 It is a very biased monarchist point of view presented as a fact. It should be attributed as such. Who was thinking that? Is it all the monarchists? A single individual? 
 *Further, the republican rebellions of 1837 – with their significant minority of conservative followers who critiqued Canada's Westminster parliamentary constitutional monarchy as both too democratic and too tyrannical in comparison to their preferred American model of checks and balances[21] – failed to inspire the majority of colonists to espouse a break with the Crown 
 This is WP:SYN. While this is probably true that a minority of republican rebels found Canada "too democratic", it does not belongs in the same sentence as the rest. Also, saying that it "failed to inspire the majority of colonists to espouse a break with the Crown" is WP:OR. The source (from the monarchist league, of course) argues that the rebellions were not against the crown itself, but against problems in the empire. But we can't conclude what is said in the article, especially since the low level of democracy at the time and the power of the army probably made many colonists to fear to support the rebels.    
 :The "democratic... tyrannical" wording can certainly be re-arranged. However, the rest is hardly OR to point out that the rebellions failed to bring about republics. Can you provide evidence that they succeeded?