At one point on an international project I had to fly a box of UK A4 to the USA in my luggage so the Americans could check their software could cope with the different size. It did, but lugging it around was a pain - paper is heavy!
I had the reverse, we had to get a ream of US Letter and corresponding envelopes sent over so we could ensure the layouts printed properly. Also some chequ… “checks” which were fascinating.
Couldn't they... just cut it according to A4 dimensions?
I wish we could buy A4 paper in North America! I find it surprising it's not available even in specialty stores. The rest of the world uses it!