You’re right about that, but other countries have similar protection. E.g. our board equivalent here in Germany would tear you a new one for. And the GDPR is gonna finish the job
Typically for the AI to do anything useful you'd copy and paste the medical records into it, which would be patient data.
Technically you could expunge enough data to keep it inline with HIPPA, but if there's more people careless enough not to proofread their paper, then I doubt those people would prep the data correctly.
ChatGPT has no burden to respect HIPAA in that scenario. The medical provider inputting your PHI into a cloud-based LLM is violating your HIPAA rights in that case.