Anna Jackson by Zariel Pate

It's the year 2100 and Anna Jackson is a black girl who lives in Seoul, South Korea. Her world is full of dragons, robots, and aliens. One day she finds a USB drive in the mail. The information on the USB informs her of what she must do, get the Crystalsphere (which is being held in China), and capture Dragon's breath in it. Then she must go to a forest in Mexico where she will find a time machine her parents built for her. She must use it to go back in time and find a Japanese man named Kazuki Sato. Together they will end the war and stop "The Great Smog" before it even happens.