Your last paragraph first: None of those functions (or many, many more) are constitutional, given the Tenth Amendment. We have them because the ever internally imperialistic power-grubbing federales have been empire building for a very long time now in a period of general constitutional illiteracy. Since we are massacring the Tenth Amendment anyhow, the good news for us greybeards is that the massacre included the creating and maintenance of Social Security and Medicare and the Interstate Highway system (even if it would have pleased Whigs).
As to Congress expelling even a single state from the "Union," the Tenth Amendment stands for the proposition that no clause of the Constitution OTHER than the Tenth Amendment is necessary to forbid such action. The only relevant question is whether Congress has specifically received the power under the Constitution to exercise itself to expel a state. The answer, as you well know, is NO.
As to Congress expelling even a single state from the "Union," the Tenth Amendment stands for the proposition that no clause of the Constitution OTHER than the Tenth Amendment is necessary to forbid such action. The only relevant question is whether Congress has specifically received the power under the Constitution to exercise itself to expel a state. The answer, as you well know, is NO. All powers not reserved to the government or forbidden to the states are reserved to the states. In order for the 10th Amendment to prevent the states from expelling one of their number from the Union then doesn't that prohibition have to be explicitly included in the Constitution? Yet it isn't there. So by your own definition under the 10th Amendment then such an expulsion is possible. Not impossible as you claim.