The American opinion on international law is that if the US isn't a party to a treaty or an international convention, then it doesn't have to follow it.

Right.  Legally the US would be under no obligation to follow it.

The US has never really been in favor of treaties unless it is allowed to exercise a large amount of control over them.  The poll suggests that Americans see a role for institutions like the UN, but the UN (to continue with the example) is too easy a target for the right wing.  Fox News commentators can point out that China is a member of this or that council on human rights at the UN, and immediately the UN will look ridiculous.

We need international laws governing human rights, but, if there is no way to enforce those laws, they're useless.  The current international legal system is a joke, in my opinion.  (And, yes, that is thanks, in large part, to the actions of my country's government, but George W. Bush is not the only problem here.)

Even if the US had signed on to the ICC, there would never come a day when a high-level US official would be arrested.  Let's not pretend that the ICC would ever prosecute (say) Bush.  As gutless as the Democrats have been in the face of the GOP, the international community has been equally gutless, and elections have done little to reverse the trend.

Be nice to America. Or we'll bring democracy to your country.