No, it’s not irrelevant, since the OP’s argument is predicated on the assumption that the rest of the world is so pitifully desparate to get its hands on US-made goods that it won’t stand up to the US over Kyoto.
It needn’t even be the exclusive provier, it might be that some US-made goods are of such significantly higher quality or lower cost that equivalent non-US products are not really close substitutes. But I don’t think that abstract arguments about comparative advantage will do the job in this case.
I’m sure that The Ryan will be able to come up with numerous examples off the top of his head pretty soon.
I’m still waiting for waterj2, who posted that figure, to come back with a cite. I’m not sure that I believe it, especially since the US has been running a balance of trade deficit for the past however many years.
Otherwise, ITR Champion, kabbes, amrussell have pretty much covered it, other than to say that, if the 25% figure is a proportion of the value of all goods (as I suspect it might be), then it might reflect the fact that US goods are more expensive than others. Also, cutting off US goods wouldn’t necessarily cause prices to rise if the non-US goods were cheaper, which the 25% figure (if it is accurate) suggests they might be.