Uniformed landscapes and pollution are two negative aspects of

American Culture

Explanation: Let's do process of elimination on this one.

1: Pop culture is just a form of media influence and entertainment so this wouldn't cause flat land or pollution.

2: Folk culture is basically the same story. It's just songs, traditions, and stories. So, this couldn't have any negative effects on the environment.

3: Indigenous Culture is like the first two and has no negative effects on the environment either.

4: Big industrial factories and littering by throwing fast food garbage and plastic in the ocean and on the ground is a part of American culture and could cause serious pollution and it has. So, this is the Answer.