Constitutionality of government obliging you to make a purchase v. taxing for it

[True Federalist (진정한 연방 주의자)]

The reason for making such a distinction does not reside in theories of individual liberty.  Indeed, many critics of a national healthcare mandate, such as Gov. Romney, will concede that the State governments have the power to mandate the purchase of health insurance, just as most States mandate the purchase of auto insurance, or many local governments require that you maintain the appearance of your property, etc.

Hence the mandate issue is at its root over whether we still have a Federal system of government in which there are certain things that the States can do which the national government cannot.

[True Federalist (진정한 연방 주의자)]

if the federal government has the power to tax, that to me implies that it has the power to do anything that is functionally equivalent to but less restrictive to personal liberty than a tax.

The Federal government does not have an unlimited authority to tax tho.  In particular, direct taxes^*, need to be apportioned in relation to the representation of each State in the House.  If an obligation to purchase something is considered a tax, then I would argue it is a direct tax and has to go through all the funky rules thereof, which clearly Obamacare does not.  (Indeed the clumsiness with which Federal direct taxes would be imposed is why they aren't.)

^* Direct taxes are those applied to the person or to property. Contrary to what most people think, income taxes were constitutional prior to the 16th Amendment, provided that they were taxes on wages or the like.  However taxing things such as rents or capital gains would be considered taxes on property and thus, direct taxes.

[True Federalist (진정한 연방 주의자)]

Thanks for the added details, CARL.