2021 Expedition with 39400 miles needs a new left catalytic converter. Vehicle runs very well. This is my first car in 50 years that needed a cc replacement.
Is Ford having issues with quality?

 

Why you need a new cat converter?
Is it under powertrain warranty still?

 

Most times there is a reason for a converter going south.
Heiko brought up a good point, there should be some warranty coverage on that.

If the cause of the converter is not determined and corrected, it will destroy the new also,,IF IT IS REALLY DEFECTIVE.

 

It is covered under the 5yr/60,000 mile powertrain. The dealership was happy to replace it but no reason for it failing was given. I'm hoping they will check on that.
Of note the check engine light for code 0430 came on a few hours after the oil was changed.

 

If the person doing the oil cge hit the wire for the O2 sensor there, it could be related.

 

Should the o2 sensor be changed with the catalytic converter? I believe it's 2 separate parts.

 

I asked this previously above: Why you need a new cat converter?
I can answer my own question for you now. It's solely based on getting P0430 code.

If you or they don't find out the root cause, you are going to have to replace your cat every year at your own expense, if you think replacing the cat or the o2 sensor will fix P0430 permanently. The cat might be bad, but guarantee can't be the root cause, there must be some other issues to go along with it for it to go bad.
hanky already mentioned the issue could be caused by whoever changed your motor oil, he must have done something intentionally or negligently to your car, you just have to go back there and pretend to blame them and just to see what they say and don't mention about dealership/warranty. You just have to find out what else they have done beside changing the oil. They might have removed your o2 sensor for inspection but didn't put it back correctly.

 

I have confronted them about why it happened on my way home from the oil change. They reported it was just a catalytic failure coincidence. I'll discuss this with them further.
Thank you for your input.