Actually, you're mistaken. The US Constitution was designed as an agreement among the 13 soverign states to delegate certain specific powers, such as coining money or making foreign treaties (a complete list is in Article I, Section 8) to a central government in order to facilitate cooperation and commerce among the soverign states.
In those delegated areas, and those areas only, is the Federal Government superior to the state governments. States may not coin money because they gave up that power willingly under the Constitution. And as clarified by the Tenth Amendment, any power that was not specifically delegated to the federal government is retained by the state.
The reason that the US can't legally levy and collect taxes on a Chinese citizen in China is not just because China has an army to stop it, it is because the Constitution sets forth the legal limits on the power of the Congress, defining its jurisdiction.
The US Congress has no jurisdiction in China, and neither does it have jurisdiction over intra-state commerce, such as that between a California employeer and his California-resident employee.
This is why the Title 26 statues and their associated regulations define a "source" of income as having only to do with various kinds of foreign and posessions commerce. This is the basis on which Larken Rose has not filed a return or paid income tax since 1997 and has yet to be taken up on his repeated requests to the IRS to prosecute him.