Some words have very different meanings on either side of the pond. So while an Englishman puts his trunks in the boot of his car before driving off on holiday, an American would put his boots in the trunk.
Similarly, an Englishman puts his pants on before his shorts.
But my all-time favourite [or should that be favorite?] only really works when spoken aloud:
In England, we pay our bills with a cheque. In America, they pay their checks with a bill.