Given most of the US population lives between Massachusetts and Florida (so would likely have more of French exposure via English and history) , and the French influence in lots of English, it's a toss up.
I certainly learned the French vert long before the Spanish verde.
You're telling me you never encountered salsa verde before learning the French word "vert"? Even if true, I highly doubt that's the norm.
And I'm not sure why you think being on the East Coast matters. 13% of Americans speak Spanish at home, less than 0.4% speak French or Cajun at home. That's a ridiculously huge region you've cited that includes NYC where you're probably going to visit a bodega long before you learn "vert" and Florida which has major Spanish influence, just like the other two most populous states California and Texas. I live about 100 miles from the Canadian border in the west, so by your geographic argument I should encounter more French than Spanish, but Spanish exposure is way more common here.