"If China only had rubber rafts and muskets, we wouldn't even hesitate to announce our intention to back Taiwan to the hilt."
We don't hesitate in our intention to back Taiwan- even Clinton proved that.
But we will not support Taiwan declaring itself independent country from China. Our security guarantees are based on premise of Tiawan and China being one country- we support a peaceful path that leads to Tiawan and China becoming one country.
Now if Tiawan doesn't want American defending it, they can declare independent and probably result in fighting a war with China and losing. But if China attacks Taiwan, then America will defend it- and result in this case will probably be that Tiawan will be able to repeal Chinese and then as result of this aggression by China, Tiawan may choose to become an independent country and in this case America [and the world] probably will support this.

"Alternatively, what I'm talking about is looking back and asking, given what we know now, was it worth it?"

I think there is no doubt that this war was worth it.
I think if costs in blood & treasure were twice as much as there are at the present- it would be worth it. But what is more important to me is how the Iraq leadership regard the Coalition's presence in their country. If there was more carnage by the Coalition forces, then that would affect how the Iraqi leadership regards our presence. Another factor is the violence cause by insurrency/terrorists if this was considerably less of a problem, then it's likely the Iraqi leadership would be far more eager for the Coalition to leave their country.
I think that the main thing that these terrorists have been successful at is increasing the dollar amount of this war- rather the lost US soldiers lives. The terrorists are mainly inficting losses of Iraqi lives- mainly making the Iraqis poorer than if they weren't under this threat of violence. These Terrorists are like disease that slows Iraq economic growth- but compared to most diseases it's more frightening that lethal or economically crippling.

"The fact that you answer "no, it was not worth it" does not imply that you think the best strategic option open to you today is to run and hide. Given that you already started the war, the best option might well be to finish it. I happen to fall into that camp -- where exactly did I argue for pulling out tomorrow? Or staying might not be the best idea; the French were right to conclude in the 1950s that holding on to Vietnam would bankrupt them, with even more dire strategic consequences for their nation than abandoning a far away colony."

The problem with French Vietnam thing is that French should have left Vietnam 10 or 20 year [at least] before they did. In Iraq we only occupied the country for short period time. There is no reasonable case to say that Iraqi govt at the moment is a puppet govt. Iraq is newly born and it's violent, but it's free.