OK, let's start with the basics:
A 'jack' is the term used to specifically describe a flag that is flown at the
bow of a stationary ship, particularly those of navies of the state.
A 'canton' is the term used to describe a quadrant of a flag but is most commonly used to describe the top left-hand quadrant of a flag in particular. Many countries have this particular top left-hand 'canton' treated differently to the rest of the flag. For example, the USA and Australia.
Countries that have a flag with a distinct 'canton' use only this part of their flag as their navy 'jack'.
The US navy jack is therefore 50 white stars on a blue field. Each star represents one of the US states and the flag is consequently also known as the 'Union Jack' a term dating back to the birth of the progenitor of the US navy, when the union was much smaller (I think the original Union Jack had 15 stars).
The answer to the question "
which other US flag has a union jack in the corner" should now be obvious. The answer is.....
the stars & stripes! Not a trick question but a fact!
The British flag is often incorrectly described as the Union Jack, when it is in fact the Union
Flag. It only becomes the Union Jack when flown at the bow of a stationary Royal Navy ship. The British flag does not have a distinct canton and countries that do not have a distinct canton on their flag use the whole flag as their navy jack, hence the colloquial use of the term Union Jack to describe the British state flag.
It is worth noting that for the duration of the 'war on terror' US warships now fly a different historic jack depicting a serpent on a field of red & white stripes, rather than the union jack, at the bow of stationary ships.
Pete
Pete
Pete
Pete