Cause freedom. Well not really, it's mostly money (as you pointed out).
You touched on a lot of things there, but in regards to traffic lights and metric system, the typical argument is "it would be too expensive to change to metric (think of all the signs we'd need to rebuild)".
Frankly, i think it's bullshit, but whatever, It's the least of my concern with the US.
As for healthcare, i really do believe there's more to it than money. A lot of people hate the idea that they HAVE to give government money that basically takes care of other people (leeches - as conservatives love to refer to them). I've never understood this mentality (i've pretty much always lived in cities), but in rural areas people have a vastly different mindset.
The thing that made me realize this was watching some series where people live on homesteads in alaska. They are 100% isolated from the world and COMPLETELY depend on themselves for survival. These people have no access to TVs or internet and pretty much the world, and they don't care. They love their lifestyles (depending on themselves and their families, living off the land, complete freedom). Then i think of the 10s of millions of people like this in the US and how they all view government as inherently intrusive. Since they get by on their own, they think everyone else SHOULD be able to as well. That is why there is so much resistance to things that seemingly make sense to the rest of us (taxes, universal healthcare, food stamps, education, whatever).
I really don't think the politicians are necessarily pigheaded, i think they are just accurately representing their constituents. The tragedy is the constituents are pigheaded and politicians learned that they can take advantage of them (lie, cheat, abuse the system for financial gain).
Then there are 'fiscally conservative' people who are educated and integrated in society and truly believe that less gov intrusion and complete capitalism is the best system. I don't have much to say about these people other than i think they're flat out wrong, but godspeed trying to convince them otherwise.