[T]he US tax system is based upon citizenship while everyone else bases it upon residence. If you have a US passport then you are subject to US taxation (you might not have to pay any because of a low income, but you’re still subject to those tax laws). It doesn’t matter where you live in the world you still cough up to Uncle Sam. The only way out of this, the only way to “avoid” such US taxation is to give up your US citizenship.
[Update 20121002: The clear implication of this passage is that citizenship is a prerequisite for subjection to U.S. taxation; and that consequently, aliens are not subject to those laws, because if they are, one could not “’avoid’ such US taxation” by “giv[ing] up your US citizenship.”] I’m no expert on U.S. tax law, but even I know that Worstall’s linkage of citizenship & taxation isn’t quite correct. It is true that U.S. income tax laws apply to American citizens abroad as well as at home; as IRS’s Tax Guide for U.S. Citizens and Resident Aliens Abroad explicitly states:
If you are a U.S. citizen or resident alien, your worldwide income generally is subject to U.S. income tax, regardless of where you are living. Also, you are subject to the same income tax filing requirements that apply to U.S. citizens or resident aliens living in the United States. Expatriation tax provisions apply to U.S. citizens who have renounced their citizenship and long-term residents who have ended their residency.
However, this excerpt’s repeated references to “resident aliens” also belie Worstall’s citizenship-taxation linkage. The category of “resident aliens,” according to IRS Publication 519, includes aliens with green cards. It also includes aliens who have a “substantial presence” in the United States while lacking either “a tax home in a foreign country” or “a closer connection to that country than to the United States[.]” Aliens outside this category are deemed “nonresident aliens” for tax purposes. Regarding the tax treatment of these two categories, Publication 519 further notes:
Resident and nonresident aliens are taxed in different ways. Resident aliens are generally taxed in the same way as U.S. citizens. Nonresident aliens are taxed based on the source of their income and whether or not their income is effectively connected with a U.S. trade or business.
Hence, even nonresident alien status does not necessarily exempt a noncitizen from U.S. income taxation. Nor is an alien exempted from these rules even if he is unlawfully present in the United States:
The Internal Revenue Code does not have a special classification for individuals who are in the United States without authorization (commonly referred to as “illegal aliens”). Instead, the Code treats these individuals in the same manner as other foreign nationals — they are subject to federal taxes and classified for tax purposes as either resident or nonresident aliens. An unauthorized individual who has been in the United States long enough to qualify under the “substantial presence” test is classified as a resident alien; otherwise, the individual is classified as a nonresident alien.
I don’t have much to say regarding Worstall’s views on French or American tax rates. It seems pretty clear, however, that his asserted linkage between American citizenship and subjection to federal income tax law is incorrect.
 Tim Worstall, Why France’s 75% Income Tax Rate Is Going To Be So Disastrous, Forbes, Sep. 28, 2012, http://www.forbes.com/sites/timworstall/2012/09/28/why-frances-75-income-tax-rate-is-going-to-be-so-disastrous/.
 Id. at 5 fig. 1-A.
 Id. at 18.
 Erika Lunder, Cong. Research Serv., RS21732, Federal Taxation of Aliens Working in the United States and Selected Legislation 3 (2008), available at http://assets.opencrs.com/rpts/RS21732_20080214.pdf.