White paint is the new black i guess so paint maintenance should remain a priority.
Sometimes brake dust especially on a white car can find its way ''imbedded'' in the car's paint surface but it does not seem to be your case...
Whatever it is likely acidic bird poop; i would strongly suggest you see a profesionnal detailer/bodyshop for advise the sooner the better
Regardless it should be completely buffed up and i would assume that it would be highly unlikely that as the clear coat is not affected. I am confident a profesionnal will carefully went sand the affected area and then buff, polish and seal the paint ideally the whole car to bring back the shine, depth and protecting the paint
Keep us posted
