I think a lot of Europeans genuinely believe in human rights and a rules-based world order.

Most people in the world have that view.

But you are mistaking the people for our EU vassal sell-out leaders here:

But they’re also cowards and want the USA to be world police

Our population is vastly against most of the US wars.
We know we're going to pay for it, first literally and later when we get 100000's of refugees they caused.

Our 'leaders' go along because it keeps the system in place of getting the crumbs from the US loot.
They don't care about the people and consequences for them.
If they refuse, as in Iran's case, it is indeed out of cowardice and the negative consequences for themselves economically.

Our economies are already in a huge crisis because of the sanctions on Russia, we suffer and the US profits from selling us expensive fracking gas.

They can not take more problems by joining this war.