At this point one has to point out that US gallons (and pints and cups and flu ounces) are different from the gallons/pints/cups/flu ounces used everywhere else

At this point one has to point out that US gallons (and pints and cups and flu ounces) are different from the gallons/pints/cups/flu ounces used everywhere else on the planet (for reasons that mostly have to do with English kings trying to get around the parliament's limits on taxation they made some gallons smaller, the US standardised on one of the smaller ones) - fortunately most of the rest of us have stopped using those units so we don't care as much, but we do have to have to be careful with, for example, US recipes. When visiting Starbucks I'm often tempted to ask the person behind the register "Venti? that's Italian for 20 right? 20 what?" they invariably will say "20 fluid ounces" .... of course the correct comeback is "I'm pretty sure they use the metric system in Italy, it must be litres, or maybe mililitres" - usually they will choose "litres"