Unless a place name is at the end of a sentence and followed by sentence-ending punctuation, whenever you list a city and a state or a city and a country, place commas around the state or the country. The rule applies even when the country or state name is abbreviated. These principles are exemplified in the following sentences:

I am from New Hope, Pennsylvania, a small town in the eastern part of the state.

I am from New Hope, PA, a small town in the eastern part of the state.

We are from Manchester, England, in the northern part of the country.

We are from Manchester, UK, in the northern part of the country.

I live in Los Angeles, California.

I live in Los Angeles, CA.

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