I believe you are correct - Computershare USA will be required even if you already are with Computershare Aus. I believe that you are also correct, will not be able to complete the USA Computershare Registration until you get the Holder ID info sent out. Not sure what Joel meant by "at any time" as I think you are correct.
I understand all shareholder-relevant contact info will be sent from Automic to Computershare as per the announcement. "Computershare will be appointed to use its intuitive management platform to facilitate a seamless transition from ASX to Nasdaq for security holders of Incannex Australia upon implementation of schemes of arrangement that have been approved by security holders and an Australian federal court." https://stocknessmonster.com/announcements/ihl.asx-3A631063/
