the separation of Senate and House has shown no glaring defect, no visible signs of failure or deficiency, no real compelling reason to warrant a change.
It appears you overlooked the New Yorker article I linked to, X-Slayer, which levels at least five criticisms toward the Senate. I will attempt to reproduce them, since no one seems to want to read it.
1) The Senate is no longer a source of meaningful legislation, only a graveyard for it. Defenders of the Senate point out that it serves a useful purpose as a check, but the problem is that it ONLY acts as a check these days. What about its positive functions? Did the founders intend the Senate only to be a graveyard of legislation, and not a wellspring of it? From the article:
“A partial list of the measures that—despite being favored by the sitting President, an apparent majority of the people, and, in most cases, the House of Representatives to boot—have been done to death in the Senate would include bills to authorize federal action against the disenfranchisement of blacks, to ban violence against strikers by private police forces, to punish lynching, to lower tariffs, to extend relief to the unemployed, to outlaw the poll tax, to provide aid to education, and (under Presidents Truman, Nixon, and Carter as well as Clinton) to provide something like the kind of health coverage that is standard in the rest of the developed world. The rejection of the Versailles treaty and the League of Nations after the First World War and then of preparedness on the eve of the Second are only the best known of the Senate’s many acts of foreign-policy sabotage, which have continued down to the present, with its refusal to ratify international instruments on genocide, nuclear testing, and human rights.”
2) Gives too much power to small states, it actively hurts big states, and diminishes the democratic representation of citizens who live in them. Remember that the 12 percent of Americans who live in the bottom 24 states are given 44 Senators – this is clearly overcompensating for the weaknesses of small states. Also refer to the above tables on state-fed balance of payments. If the Senate only leveled the playing field for small states, as some assert, then these accounts would be equal, or the big states would only run small surpluses given their influence in the House. But the Senate throws things off so utterly, that small states uniformly run surpuses and big states like CA, NY, TX are bled dry. For those who defend this function, please consider the questions: How much power should the small states have, and how would we know if they had too much?
**3) States’ rights are not more important than citizens’ rights. When the residents of say, Iowa, are routinely priveliged over millions of Californians and New Yorkers, you must have a very compelling reason to abridge the democratic process. ** Alexander Hamilton: “As states are a collection of individual men, which ought we to respect most, the rights of the people composing them, or of the artificial beings resulting from the composition? Nothing could be more preposterous or absurd than to sacrifice the former to the latter.”
4) The two-Senators-to-a-state rule was a result of threat, was not a guiding principle of the founders, and should not be defended as such. Once again, from the article: “Dahl notes that Gunning Bedford, Jr., of Delaware, told his fellow-delegates to the Constitutional Convention that, unless the big states yielded, “the small ones will find some foreign ally of more honor and good faith, who will take them by the hand and do them justice.” The Senate was formed less by rational argument than by threats of treason and war.”
5) Empirically, other countries are reluctant to use our system as a model. With our global influence, you would think there would be more countries with similar constitutional setups. But most democracies are parliamentary (anyone want to look this up?) Countries that have adpoted it, like Brazil, find the legislative process to be incredibly conservative. Their Senate, like ours, gives tiny, rural conservative states great power over the hugely populated big three states. The result – small states bleed the big states dry, and useful reform always dies in the Senate. Another result is that the executive branch has to pass most laws by executive decree that go immediately into effect, which then come before the legislature in 90 days. A further rule is required that the entire legislative process shuts down if the Congress does not vote on the decrees. All because the Brazilian Congress, modeled on ours,can’t get positive legislation enacted, serving much better as a killer of it.