Compared to you guys (Swiss Federal Constitution: ratified 1999) we aren't even driving horse and buggies. We're on some wobbly farmer's cart pulled by a mule.
The thing is - as you say - it's important to not be dogmatic about these sort of things - and dogmatism often seems to me part of the American way unfortunately. While the latest amendment to the US constitution apparently has been passed in 1992[2], the constitution has never been completely revised. Noone seems to even propose such a thing, since the 'founding fathers' obviously haven known best. Many shortcomings, like the election system and the lack of direct democracy, seem to go back to the limitations of information travel and organization back in the late 18th century. Others, like the president's veto power, are stranger, since the idea of a clear separation of powers go back to well before the founding of the USA[3] - it's hard for me to explain how George Washington was able to get this through, but it seems obvious from a European, French Republic influenced standpoint that it doesn't belong there. And the ability of the speaker of the house to block a vote? Come on, that's a systemic bug that should be squished with the reaction time of a Microsoft hotfix.
[1] http://en.wikipedia.org/wiki/Constitution_of_the_Athenians
[2] http://en.wikipedia.org/wiki/Twenty-seventh_Amendment_to_the...
On a related note: In the light of recent history I more and more come to believe that exactly these checks are what's missing in the USA. We Europeans have a lot to thank the Americans, first of all the Republican system they pioneered - however our nation founders have gradually improved on their template. It'd be about time for them to roll out version 2.0, based on all the things that have been learned about shortcomings. Step one would be to not allow a single person to completely blockade a political process in congress.