Many horror films start out well, but fall apart about halfway with some reasoning which no one can understand.
US is very different, it’s a psychological horror film that has something to say, which may open minds and cause US to discuss what it means.
The story involves a family - husband, Gabe Wilson; wife Adelaide and their two children, Zora and Jason.
When Adelaide was a youngster, she was left with her father, while her mother uses the restroom at a beachside amusement park at night. The father was playing whack-a-mole and drinking beer, when Adelaida wanders off. She goes on the backside of the carnival where she enters a hall of mirrors.
Within the creepy amusement house she comes in contact with a doppelganger (an apparition or double of her). Once she’s located and taken home, she is unable to speak.
Back in present day, she and family go back to the same beach for some down time. She’s apprehensive, but now that her voice is back, and she’s grown, thinks it’s silly not to go.
However, there’s a lot to US (which may stand for United States), it’s use of scripture, specifically Jeremiah 11:11 — “Therefore thus saith the LORD, Behold, I will bring evil upon them, which they shall not be able to escape; and though they shall cry unto me, I will not hearken unto them,” and the philosophy that everyone has two sides, one good and one bad.