I must admit that I don't see this as black and white, common sense tells me that the US are prepared to go against the rest of the world to enforce their position, and I also think that this is the result of Israel calling in some favours. If anyone is going to precipitate a crisis, it'll be Israel. If the US bombs Syria, then Israel can say to their enemies -- of which there are a few very close by -- "See what happens when we snap our fingers? Back off or it'll be your turn."
But the other side of this is that these are people just like us. Fifteen years ago it was Bosnia looking for help, and in the end NATO (legally) took action against Serbia. Back then this was personal enough to me that I could celebrate the NATO bombing. You can see why this was personal to me
here at the Wayback Machine, which remembers everything every put on the web....
This issue is too common to worry about being the end of the world -- it could be a step forward, depending on the outcome, and I don't mean what happens in Syria. If the world accepts what the US is planning without any censure, then it'll definitely be a dangerous step backwards. But I don't think they will -- the UK were the 'voice' of the US last time, with their honest British accents assuring everyone that the WMDs must be dealt with -- and they learnt a sharp lesson, which they didn't fall for this time. Good on them.
Any nation offering 'moral' support is effectively giving away their right to censure when things go horribly wrong. It's really saying hey, it might be illegal, but it's right. That's a big decision to make, and really gives the US a lot more leeway than any nation should have.
The US have already deployed the ultimate WMD. I guess that gives them a certain perspective. But it's a bit close to 'nobody has the right to have too much power... except us.'