As a true American, I shall take up the task to answer this important inquiry!!
We usually don't mix the peanut butter and jelly (not jello!) together, but instead we slather one side of bread with peanut butter and another side of bread with jelly/jam and put the two sides together and eat as a sandwich. It's a childhood favorite for many of us, but an acquired taste for international people.
As another red-blooded American, I agree with this statement. Whenever I see people mixing the two in movies it messes with my brain. Like who does that? Almost as weird as putting milk first in a cereal bowl.
The most popular jelly/jam flavors are strawberry and grape. Smucker's is popular.
Also, I don't know a lot of people who buy the jar with both peanut butter and jelly. Yes, it exists but people don't buy it.
The bottom part of my reply is missing: more controversy...
Some, Americans, with odd tastes, will prefer crunchy peanut butter over creamy. And most likely will go with the usual choices of strawberry or grape jelly.
Fun fact in America: jelly, jam, and jello are three different products, but still made with fruit.
personally when eating pb&j i spread out the peanut butter onto both sides of the toast and then put a dollop of jam over on each side as well because i like a lot and so it's even, i'm not really mixing the two but it's basically going to mix anyways when you smash the two pieces of toast together lol. i always use jif (brand of peanut butter) but these days i use skippy, totally recommend it's real good. for jam i've never branched out, it's been smucker's since day one
Do you, americans, mix peanut butter with jams? when putting it on bread/toast? Or is it like just a movie thing?