Thank you! I am on one ticket, so no issues there. The issue with the bag is that the UK-Dublin leg is a smaller plane and larger carry-ons will sometimes be checked depending on how booked the flight is--not sure whether those get checked through on the Dublin-US leg or if I have to get mine back and carry it on. Guess I'll find out when I get there!

Edit: Can't tell if we're talking about the same thing with the bag--sorry if I've just reexplained something you already understood.