What is the difference, if any, between 'porn' and 'porno'?

I had never thought of a potential difference between 'porn' and 'porno' until I encountered the following dialogue from Family Guy Season 9 Episode 9(thanks to FumbleFingers for reminding me the correct TV show and episode):

Priest: Leave this House of God!

Lois Griffin: But... But I love the Church! It's an important part of my life!

P: Maybe you should have thought of that before you made a porn!

L: But Father, I didn't mean - wait, did you say 'a porn'?

P: Yes.

L: Oh... Well, that's kind of weird.

P: Why?

L: I mean, you either say "You made porn" or "You made a porno". You don't say "made a porn". It just... it hits the ear wrong.

This implies that, as a noun, porn is uncountable meaning pornography in general, and porno is countable meaning a pornographic movie/tape.

Both Merriam-Webster and The Free Dictionary define 'porno' as a perfect synonym for porn. The Urban Dictionary isn't of much help either: the first six definitions are jokes, and the seventh says that it's just another way to pronounce 'porn'.

So,

• Is there any difference between 'porn' and 'porno' or not?

• Can both be used both as a noun and an adjective? (if yes, provide examples, please)

• Can either of them be used as a countable noun? (if yes, provide examples, please)

• Are there any differences specific for American, British or any other variety of English?

Per OP's revision, it's from Family Guy, Series 9 Episode 9, titled "And I'm Joyce Kinney" where Lois makes a porno and shows it in church. The word porno in the sense of a single instance of porn (i.e. - a video, in this case) occurs repeatedly in the episoide - for example, Brian says "Lois! You were in a porno?".

Seth Macfarlane (creator of both Family Guy and American Dad) has an excellent ear for language usage, and I have the distinct impression he likes to raise little quirks like this. Probably with all the success he's having, he actually has people around him actively seeking out such tidbits for him to consider using in his cartoons.

Digressing slightly, I think there's a reason why "quirks of English language" occur more often on "adult cartoons" than we might otherwise expect. Native speakers subconsciously "know" much more about usage than they're normally consciously aware of. When you see something like OP's example, there's a strong tendency to think "Yeah! I know that too! I'm smarter than I thought!". You end up feeling good about yourself when you watch it, so you're up for more of the same.

Regarding the specifics of "accepted usage", Lois is correct that "a porn" is, well, weird, - "porn" is an uncountable mass noun ("The Church disapproves of porn"), or an adjective ("Lois made a porn video"). Sometimes "porno" is used as an adjective too, but never a mass noun - usually, it's a countable noun ("Brian made several pornos", each a single item of pornography). A porno is normally video - I've never heard it used of pictures, writing, audio recordings, etc.

The difference is slight but real. Since these words are more often heard than read, I'll have to give you the benefit of my own experience of having heard the terms used in speech.

Porn can refer to pornography in the aggregate or as a mass noun to cover multiple instances of pornographic media. Porno usually refers to a single instance of a pornographic film or publication.

Because parts of speech in English are mutable, nouns can be used as adjectives, verbs as nouns, nouns as verbs, etc. So you could talk about "a porno" or "a porno film" or "a porn film" or "porn films" or "some porn" or — well, you get the idea.

Completely anecdotal and unsupported, but I never heard either "a porno" or "a porn" except on US television. Growing up in my area of the UK in the 90s, the term was "porn" and it was an uncountable mass noun, like "poetry" or "photography". Things appear to have changed, though, and there's even a UK podcast entitled "My Dad Wrote A Porno".