The fact is, of course, that more than 99% of historical governments have been violent impositions. Even if you believe that the modern state is legitimate and wields genuine authority, you will surely not believe that this was the case in more than one or two nations before the mid-19th century. (David Hume famously savaged the view that living within a country's borders constitutes tacit consent to its laws on the ground that there was simply no alternative for most people; his argument does not have quite the same force today in that it is "merely" extremely difficult, rather than impossible, to emigrate, for most people. In any case, tacit consent has critical problems). Perhaps for utilitarian reasons they might still have been justified on balance, but there were still many state actions with no possible utilitarian justification.
This all seems fairly obvious once you think about it, but I suspect it is something we do not really think about. Historical figures are still referred to as Kings and Queens as a term of honour. We take pride in the past successes of our countrymen at subjugating foreigners through military force. Being a Princess is seen as dreamy and romantic, rather than being a way of living off industrialised theft. I suspect a lot of this is due to the sentiments discussed in Daniel Klein's magnificent The People's Romance: Why People Love Government (as Much as They Do), although there are plenty of possible contributing factors. Existing states have little incentive to promote the view that past states were illegitimate and people would have been justified in resisting them, since it could easily lead to more people questioning the moral foundations of the modern state.
Here's another question: suppose you believe the modern state to be legitimate, but accept that the historical state was a violent, coercive and ultimately evil institution. At what point did the transition come? I ask this not as an attack on the modern state, merely out of interest. Obviously the answer will depend on what you personally see as the justification for the state. The most obvious answers for the UK would be 1215 (Magna Carta, although this is very shaky for anyone below the rank of baron), 1485 (end of the Wars of the Roses, one of the most visibly destructive and anti-utilitarian consequences of British governance), 1832 or 1867 (First and Second Great Reform Acts, to improve democracy), and 1908 or 1945 (the People's Budget and the introduction of the Welfare State, for the more Rawlsian-inclined thinker).