When Americans think of “Hispanics” or say someone “looks Hispanic” they are talking about mestizos.
“Hispanics” out west tend to live in neighborhoods with whites, unless they are recent immigrants, something I’ve noticed in my travels out there.
Yes, the Celts overran Europe— Spain, southern France, northern Italy, all over. Then Spaniards conquered the “new world” and the French took the Louisiana Territory and parts of Canada. Hence, “white Hispanics” have more in common with the Scots-Irish of Appalachia and Cajuns of New Orleans than the aboriginal natives of the Americas.