Awaiting your approval, I'll at least tackle some of the questions you asked me, that you seem to have at least partially understood.
Surely you reinforce the notion that the political institutions are rigid, inflexible and unable to change with your own discourse.
No I do not. In fact, if they were so unable to change, how could we have a constitutional convention that completely bypasses Congressional approval? (see Art. V)
Aren't the citizens in DC and the territories in the same boat?
No, they're not. Again, read up a little more on the American Revolution. Again the British overreacted by stripping the colonists of what they felt were their rights as natural born
Britons. When Parliament & the King took away these rights in response, it stirred up a hornet's nest. It was, again, about a lot more than taxation.
Dick Lamm is also entitled to his opinions, which I find pretty daft. Wyoming gets the same 2 votes in the Senate as California--fact. But then again, Colorado has a population smaller than Maryland's and has one less congressman than we do. He should be supporting the Senate instead of lambasting it. Colorado also gets the same two votes as California, with a mere fraction of its population. What the hell is he complaining about, having been governor of Colorado? He says we should have picked the parliamentary form--opinion. I may also remind Mr Lamm that Australia is a parliamentary democracy but its federal system resembles that of the United States--their upper house, the Senate, has an equal number of senators for each of the six states, 12 of them, elected half at a time (just as the US Senate is elected 1/3 of its membership at a time). In fact, it was established this way in the very year he mentions: 1900. There are other parliamentary democracies which employ that sort of strong federalism (strong federalism not meaning in this case a powerful centralized government, but the opposite, or at least a "balance of power" between the two levels of government, regional and national/federal). Canada has such strong federalism, it has a weaker central government than the US, it simply achieves it in a different manner than the US does it. And in 1787, modern parliamentary democracy, as it existed in 1900 or today, did not yet exist. What an idiot. [Gov. Lamm, not you.]
As for arcane rules. The super majority and the filibuster for one. There are dozens of procedural rules, including holding up POTUS nominations, and budget practices like inserting budgetary items as a privilege..
What supermajority rules? Can you be more specific, as I asked, on which rules/procedures in the U.S. Senate require a supermajority? Your quote did not cover that. Oh, and you cannot filibuster POTUS nominations anymore. Don't you remember the infamous nuclear option?
Any effective form of government has to be responsive to its citizenry. When an institution becomes rigid and inflexible it cannot. My purpose in picking on several "easily" changeable areas is to demonstrate that if they can't be changed.... then what can? (Your optimism in this topic, is what I challenge. Your ideas for change are often appealing.)
Well thanks, it's not often I get a compliment from you.

But yes, they can be changed. State governments have done so, and again, there will be a national convention, provided a few more states apply for it. The mechanism for the changes is there, Ricky. It can totally bypass the moribund Congress you often talk about, and the amendments it proposes do NOT require congressional approval. The authors of the constitution of 1787 included this mechanism to bypass Congress for this very reason. Over time, flaws in the constitution have been fixed, and sometimes, pretty quickly. (Like in 1800, an amendment was proposed soon after the great fiasco when Jefferson and Aaron Burr tied in the electoral college and the House took 36 ballots to decide the issue. Later that year, Congress proposed the amendment fixing it. It was ratified within a few years.)
But should the constitution be too easy to change? A quick glance at the constitution of Maryland, for example, or any state for that matter, will show you what happens when it's too easy to repair. The result is just as disastrous.
Sorry, I could not find the pdf version I had found before but here it is in hyperlink (or whatever it's called) form. Take note: it is 108pp long:
http://msa.maryland.gov/msa/mdmanual/43const/html/const.html