(As in, the difference between American English and British English.)
We DO have fries here in Britain as well. When we have “fish and chips”, it’s not battered fish and French fries; the chips are thicker cut, more like unflavoured potato wedges.
In McDonalds, we have FRIES and burgers. We know them as fries. Fries are the thin, noodly kind!
They’re not the same thing and can’t always be used interchangeably!