How to end a war when your ally refuses?

[TechnoGoth]

So I hit what feels like a bug or at least a badly designed mechanic.

I'm currently in a defensive war as Mexico against the USA. The USA is willing to accept a peace deal with me but because my AI ally has vast gold reserves and I'm pretty sure has not done anything in the war they are refusing to accept a peace deal. They have 0 war enthusiasm but still have -140 acceptance to even a white peace.

Is there away or force them to agree or negotiate separately?

Or is my only option to surrender and let the USA take their war goals?

[The Former]

If they have 0 war enthusiasm, I'm shocked they haven't surrendered independently yet. I thought that was the way it was supposed to work.

Short of them doing so, the only thing you can do is try to make the deal more lucrative to their war goals and hope the US accepts. As was the case in the era, all parties who have a seat at the table (not all parties will; minor powers who aren't recognized won't) must agree on the terms of peace.

[TechnoGoth]

I think the problem is that since my AI ally is separated by water and have no navy they haven't sent troops to fight and have no casualties. So it doesn't trigger a willingness to make peace. And since they have no war goals I can't offer them something in the peace deal.