Do you state this from experience? You have eaten both?
Obviously, the raw vegetable used as an ingredient is some species of potato.
Amurican “French Fries” are an extruded product. Potatoes are skinned, mashed, and cooked in industrial sized batches of smooth glop. The “masa” (the technical term for the mix) is processed through an extrusion machine which produces the precise, unvarying, cross sections of the French Fry. The lengths are randomized by the cutting wires that trim the extruded product to length.
The remaining steps are to batter the pieces and then flash freeze.
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I like to hope that British Chips are potatoes, cut into wedge shapes (chips; like wood chips), battered, then immediately fried.
Never frozen. Never processed into a gooey mush.
(But IDK maybe Amuricanization has ruined the chip.)