A bun with a cooked chicken breast as filling would generally be called a chicken sandwich in the U.S., but in the UK and other Commonwealth or former colonial countries, such a dish is not generally considered a sandwich, and would generally be called a chicken burger instead; most North Americans would not consider such a dish to count as a burger, since Americans generally consider a burger to require a patty made from ground/minced meat.

For sandwiches, being cold is usually key in Non-US english

In the UK and Australia, the term sandwich is more narrowly defined than in the US: it usually refers to an item that uses sliced bread from a loaf. An item with similar fillings but using an entire bread roll cut horizontally in half, is generally referred to as a roll, or with certain hot fillings, a burger. However, hot sliced (not ground) beef between two slices of toasted bread is referred to as a steak sandwich: the sliced loaf bread distinguishes the steak sandwich from a burger.