I'm White Hispanic with blue eyes; my roots are Spaniard and Italian.
I once took a road trip in the nineties along the border between Mexico and the U.S. with three other people: my step-father (same ancestry), and two other (pretty white, but maybe a bit more olive, I dunno) dudes (his friend and that friend's son). Both of them were born in the U.S., my step-father had had his U.S. citizenship for years; I was the only one who was an immigrant.
Every time -- and I do mean every single time -- we crossed back from Mexico to the U.S. (we did it like five times, it was the point of the road trip), they were asked for their papers. I was not. In at least two occasions, when my papers were offered, the migra officer waved it off, because it was unnecessary.
White is absolutely about the color of your skin and the way people identify (or don't) with you in the U.S. It was like that back then and it's still like that now (my brother can attest). Being of Italian or even Spaniard blood does not make you some swarthy POC and I really wish a lot of the people who look like me and are from the places I am and my ancestors were from would recognize that.
P.S. There's white people in Mexico and Brazil and Venezuela and Uruguay and Colombia and Argentina and... I'm not gonna list all of South America, but just shove it all together. A lot of us are from the same ancestry I am (usually a lot more Spaniard than Italian; in Brazil a lot more Portuguese). There's racism all throughout South America -- based on skin color, based on provenance, based on who your parents or ancestors were. And at no point -- not a single fucking moment -- has being on the white side of that not benefited me, nor a single moment in which being a POC has not harmed my friends and other people.
Just, you know. Public service announcement.