The True Meaning of Smekday by Adam Rex

From chapters.ca:
Gratuity Tucci (call her Tip) gets a fairly early start behind the wheel. She's 11 - and she's good if you want to know. Plus, laws don't matter too much these days, and Tip is desperate to find her mom who was abducted by aliens on Christmas Eve (technically "Smekday" Eve since the Boov invasion). So while the rest of the American population gets shipped via rocketpod to Florida - the proposed new "United State of America" - Tip heads south in the family car to search for her mother. On the way, she meets a solitary Boov mechanic named J. Lo. He's unarmed, and he can fix her battered car (make it fly), so she agrees to give him a ride, which leads to two alarming discoveries. One is that J.Lo turns out to be not so bad. The other is that J.Lo is #1 on the Boov's most wanted list for making the hugest mistake in the history of Smekland (or "earth" depending on your point of view). Now Tip and her many- legged friend are the only ones who can save the planet from a really big catastrophe.