I wonder why "in" is placed between "painted" and "the words." Also, is "in" necessary here?
Native speaker’s answer
Rebecca
"In" is a preposition for "the words of our country's call for justice", which is a noun because the "words" are a physical thing (because they have been painted), and it is an idea. "In" is the preposition that is used because it describes something that is "enclosed" or "surrounded" by something else, and here the "streets" are "enclosed" by "the words of our country's call for justice" because those words have been painted on the streets. Therefore, "in" is necessary here.