Ok, I'll admit that I horribly described the debate there by saying overturn that phrase since its not binding law, but it was the basis for the arguement about the legality of slaves and why the constitution so closely tiptoes around and avoid the issue. Since nothing actually states the legality directly of slavery we can look to both the Federalist papers and Declaration of Independence as a reference of interpretation and context. And yes they do address representation for slaves, but not the explicit legality since states never would have come to agreement at the constitutional convention if it was decided one way or the other, which indirectly leads to the civil war later.
And yes, states rights were dramatically decreased by the large interpretation of the interstate commerce clause, but the states still retain plenty of rights. Perhaps the most overstepping parts being the feds ability to enforce illegal drug laws and the issue now with how much influence the government can give to states with regard to abortion. However, most of that has absolutely nothing to do with the civil war.
As for the 17th Amendment, it means that the people need a say in choosing their senators. Sure this does take power from state legislatures, but it is still up to the state to decide how the senators are chosen. As long there is some form of election by the people the rest of the decision is left up to the states, from how the election takes place, to what decides it to who makes it on the ballot. Besides, it was the states who initially gave voting power to the people and many states already had senatorial elections before that amendment was passed. That amendment was the result of states influencing the national government. Washington is an interesting study in election type, which recently had upheld in the Supreme Court that they can put only the two top candidates from the primary on the ballot even if they are from the same party.
