Is a Comma Necessary in Spelling Out Locations?

Which sentence is correct?

1. She graduated from the University of California, Davis, in 2020.

2. She graduated from the University of California, Davis in 2020.

Similarly:

3. We visited their Arlington, Virginia, home.

4. We visited their Arlington, Virginia home.

According to Merriam-Webster's Guide to Punctuation and Style, #1 is correct, while #3 is preferred.