The first step to wisdom is calling things by their proper name and the definition of extortion does not include whether you like the mafia who is extorting you.
Well, yeah, you're right, and I don't recall ever invoking the notion of liking the mafia. Since your argument is so heavily predicated on the definition of extortion, why don't we look at how it's defined?
ex·tor·tion [ik-stawr-shuhn]
1. an act or instance of extorting.
2. the crime of obtaining money or some other thing of value by the abuse of one's office or authority.
3. oppressive or illegal exaction, as of excessive price or interest: the extortions of usurers.
4. anything extorted.
ex·tort [ik-stawrt]
1a. to wrest or wring (money, information, etc.) from a person by violence, intimidation, or abuse of authority; obtain by force, torture, threat, or the like.
1b. to take illegally by reason of one's office.
2. to compel (something) of a person or thing.
If this is going to boil down to a semantic shell game then consider me out, but it's completely nonsensical to claim that the act of being taxed in general is akin to being extorted. Now, there are some instances where taxes are definitely used as an oppressive vehicle to subjugate a certain group or class of people (see: the Leibzoll) and/or to reap the benefits of laying claim to a declared colony/territory, but that brings us to the next part of your post:
The point is not that we have an elegant phrase to describe something when it pains us to recognize the truth of the matter, but that the great earth makes no claims over who owns her land. Sovereignty is not some esoteric contract bestowed onto legal fictions by god himself but a matter of great contention, especially when you live in a world of people who only recognize the sovereignty of the state, backed by guns and run by people who neither created nor conquered the land they rule nor pay for the debts they accrue in your name.
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My contention is not with governance in general, my contention is with the nation state as an institution. The nation state has me paying for wars fought hundreds of years ago and asks me to feel privileged that I didn't grow up speaking French, wars which would not have been funded without an extortionist infrastructure to perpetuate it's sociopathic blood thirst. Wars should be fought to destroy these things, not to maintain them.
Your issue here is the legitimacy of state structures, which is an issue intimately tied to the question of sovereignty. Any sovereign state exists because it is legitimate -- it fulfills its primary responsibility, which is to guarantee to act within the best interests of its people. When the state acts in an illegitimate manner, by definition, the people reject what is deemed as an illegitimate use of authority; when a state is deemed illegitimate, by definition, the people reject the government: the sovereignty is revoked by the people. All wars essentially boil down to the question of sovereignty and thus legitimacy, which you rightfully add as a question of great contention. When the Crown refused to recognize an independent America, they fought a war over it. When the Crown refused to entertain the notion of an independent Scotland, they fought many wars over it. In other words, they refused to accept the legitimacy of these rebellious power structures because it defied their decree of authority. In turn, they fought these wars with funds that were collected by the people -- the people must be taxed because governments cannot function without it. When the government cannot function, it cannot fulfill its duty to serve the best interests of the people. One of these pivotal functions is the enforcement of authority in order to maintain and/or expand a claim of sovereignty -- state powers are not so quick to surrender their legitimacy, whether that threat be internal and/or external. You are correct when you say moving is not a simple solution: this is indeed a phenomena found in a great majority of the world with only a mere handful of exceptions. Thus, your notion of overthrowing perceived illegitimate power structures is a never ending cycle of violence and revolution, because you're asking to destroy a core function of any functional nation state.