Last weekend we actually visited Caernarfon.
Maybe we were there at the same time! I think we were there on Sunday, or darn close.
I can totally see the anti-English thing happening, I guess it's one very small place where it's good to be American. The locals were super nice to us and went out of their way to teach us a bit of Welsh or tell us about stuff. It's a shame they weren't nice to you.
Beaumaris really reminded me of Sausalito and Beddgelert felt a lot like Estes Park in Colorado.
One other thing, the Air BnB actually came with 2 cats. We had to feed and water them and they sat on our laps and purred. It was nice for my boy, who has never been allowed to have dogs or cats. I'm not sure about the ethics of leaving cats as part of the rental, but we certainly took care of them.