It's not clear why you are filing a CA non resident return.
Your statement "no state can tax an IRA received by a nonresident" is probably not correct. Technically, it's more like "no state can tax an IRA distribution received by a full year resident of another state".
If you're required to file a CA return as an ex-pat, then your IRA is probably taxable by CA.
See:
State tax on expatriates
https://ttlc.intuit.com/community/state-taxes/discussion/re-do-expats-need-to-file-state-returns-if-...
https://ttlc.intuit.com/community/state-taxes/discussion/what-is-my-state-of-residence-if-i-don-t-li...
https://ttlc.intuit.com/community/state-taxes/discussion/re-il-state-taxes-living-in-spain/01/237630...
https://www.greenbacktaxservices.com/blog/tax-for-expats-state-taxation/
