On the federal amended return attach to the front of Form 1040X any documents that support changes made to your original return. Therefore, you will need to attach your corrected Form 1099-R. please view pages 18-19 in the link below to view assembly instructions for Form 1040X.
https://www.irs.gov/pub/irs-pdf/i1040x.pdf
According to the California Schedule X instructions, you need to attach your federal schedules to show changes made to your federal tax return and the corrected 1099-R to support the changes made.
Please view the link below for more information.
https://www.ftb.ca.gov/forms/2018/18_schxins.pdf
