The status of the USA as a dependable high contracting party was damaged though by Kyoto. Not because it didn't ratify Kyoto, but because it never had an intention to make steps for ratification. It's the difference between not being able to ratify according to your own constitutional rules (which is a legitimate reason to withhold ratification) and having no intention to ratify to start with (which basically makes you a cheat).
Now, nobody will forget that the US is the pre-eminent power in the world. But the fact that Kyoto still hasn't been forgotten also tells us something about the extent to which other high contracting parties trust the US.