Any chance of pictures? If twigs still haven't leafed out I'd assume they're dead. Are there any buds? Are they dry and fall apart if you rub them? Do the twigs snap when you bend them?

I'd wait until next season just in case, but w/me having the same damage on a number of trees both this year and years before, it's unlikely that those twigs/branches will recover.

I grow red twig dogwood and get the occasional branch or portion of branch that never fully leafs out and I eventually give up waiting and cut them off, but I do think they‘ll leaf out normally next year if they’re left alone. I’ve also got an American dogwood that has the problem this year! That’s never happened with this tree before and it’s at least 20 years old. We’re 1.5 years into a run of bad weather and it’s showing in a lot of plants. I even lost hostas this winter!