I can confirm that chili (and bell) peppers are new-world plants. They got the name "pepper" as an analogy to the main source of spiciness, black-pepper, which is from an old-world plant.
In fact I believe the only nightshade used as food in the old-word was the Eggplant, with potatoes and tomatoes also being new-world.
So prior to 1492, there was no tomato in Italian food and no chili in Thai food.
Old-world food was a hell of a lot more boring before the Columbian exchange. It transformed food so much that most of what we think of as "traditional" cuisines in various old-world countries or regions are largely products of the 16th century or later.
The exchange also cut the rate and severity of previously-regular famines dramatically, enabling a huge population boom and economic expansion (see: Mann's 1493). Mainly due to maize and potatoes, maize being incredibly efficient on a calories-per-acre basis, and potatoes being stupid-easy to grow almost anywhere, having decent caloric content and not-bad nutrient profile (gotta eat the skin, though) and being easy to store for the medium-term to cover gaps when other crops fail (you just... leave them in the ground)
> Old-world food was a hell of a lot more boring before the Columbian exchange.
Turnips. It was mostly wheat, barley, and rice with a side of turnips. Not the modern turnip that’s been through 20th century breeding for some semblance of flavor, mind, but an “heirloom” variety that is even more boring than turnips are now. The only flavor worth mentioning was in the leafy parts.
In fact I believe the only nightshade used as food in the old-word was the Eggplant, with potatoes and tomatoes also being new-world.
So prior to 1492, there was no tomato in Italian food and no chili in Thai food.