Is a separate US-based QBO Accountant account required to set up a client on QuickBooks Online US (USD/US sales tax), or can Canada QBOA do it?

You'll need a QBOA US account with a different email address to manage QBO US accounts. You can ask your client to help you sign up for a QBOA US account and transfer access to you later.

Hi, Navpreet.

I wanted to let you know that it appears you have already posted this on a separate thread, and one of our colleagues was able to provide a recommendation.

 Visit this link to see the response: https://quickbooks.intuit.com/learn-support/en-ca/other-questions/re-can-my-canadian-qbo-accountant-login-create-manage-a-us-qbo/01/1594599#M26539