> I also don't think the rate at which amendments are proposed is a good indication of how healthy our country is. Shouldn't things stabilize and require less revision eventually?

I don't think that's obvious at all, especially given changes in population, technology, and international situations over the same timeframe as that nation's institutional stagnation.

The two party system is outdated. While Democrats fight for unlimited abortion up to birth, republicans fight to end the world. There's no sane middle ground. There is political room for a third middle party.