American federalism off balance?

In the fifth chapter of my book, I allude to the passage of the 17th amendment to the US Constitution as part of a larger effort to democratize more thoroughly the American political system. This amendment provided for the direct election of Senators. Was it a good idea or not? Bruce Bartlett argues that it was not in "The problem with the 17th." Bartlett believes that the 17th amendment effectively upset the careful balance that is American federalism. He further argues, with less plausibility I'm inclined to think, that it paved the way for the huge expansion of the federal government in the mid-20th century. Here's Bartlett on the procedure replaced by the amendment:

Few people today know that the Founding Fathers never intended for senators to be popularly elected. The Constitution originally provided that senators would be chosen by state legislatures. The purpose was to provide the states -- as states -- an institutional role in the federal government. In effect, senators were to function as ambassadors from the states, which were expected to retain a large degree of sovereignty even after ratification of the Constitution, thereby ensuring that their rights would be protected in a federal system.

The role of senators as representatives of the states was assured by a procedure, now forgotten, whereby states would "instruct" their senators how to vote on particular issues. Such instructions were not conveyed to members of the House of Representatives because they have always been popularly elected and are not expected to speak for their states, but only for their constituents.

Bartlett is not the only person convinced that this amendment was a mistake. So is Ralph A. Rossum, in Federalism, the Supreme Court, and the Seventeenth Amendment: The Irony of Constitutional Democracy. Furthermore, there are a number of groups in the US dedicated to the repeal of the 17th amendment, mostly to defend states' rights and curtail an overweening Washington.

Although it's not clear to me that repeal will have the effect its proponents think it will, they have nevertheless called attention to a legitimate feature of federal systems, viz., the need for representation of the constituent governmental units at the federal centre. Here in Canada our Senate on paper represents the provinces, but the fact that our Senators are effectively appointed by the Prime Minister negates this representative character. Americans have the enviable luxury of debating whether state legislatures or the state's voters should elect Senators. We haven't got even that far in this country. In many respects, Canada is more decentralized than the US, with the provinces jealously guarding their interests. However, our upper chamber does not adequately represent these interests in Ottawa. In fact, because of the way its members attain their seats, the Senate has become one more arm of what many would see as an already excessively centralized prime ministerial government. Although Senate reform is a cottage industry among some academics and pundits, it has yet to go anywhere despite several false starts. Our neighbours to the south are considerably ahead of us on this score.