Juxtaposition:

Main Entry: jux·ta·po·si·tion

: the act or an instance of placing two or more things side by side; also : the state of being so placed

  Used in MY sentence:

The juxtaposition of my 2 year old melting down in her carseat in the backseat and the uber-sweet “Have Yourself a Merry Little Christmas” on the radio was too much for my sleep-deprived brain to handle while driving in traffic.