Enforcement of that law must by its very nature be a federal responsibility. It has to be to stop tax evaders.
It is a problem that goes back to the founding of the US.
There has never been an adequate way of funding the USG, even a very limited federal government. Constitutionally, the federals are forbidden from directly taxing the states; yet they cannot leave individual taxes up to the states to carry out, because individuals cross state borders all the time to evade federal taxation, even now. States have to go to lengths to catch people who have left the state to evade state taxes.
Yet about any direction you go with this, it works to the advantage of authoritarian-totalitarian types.
A totally federal taxation structure means “federalizing” all citizens, which has been in play since Social Security; as well as national ID cards; the weird restrictions of monitoring all financial transactions; it just gets icky, which it is.
Taking money at a higher level, such as VAT, would always be promised “instead” of income and other taxes, but the truth is that they would institute the VAT and *keep* the other taxes as well. The same with a national sales tax.
The bottom line is that taxation is a minefield, and millions of money people are employed specifically for the current system, so have a strong inertia to change.