You can, but you really shouldn't use Mario Kart Live: Home Circuit outside

Nintendo and Velan Studios don't want you to use Mario Kart Live: Home Circuit outside. The box for the game specifically says the toy is for indoor use only. The thing is, there's nothing about the product itself that prevents outside play.

If you really want to, you can take your Mario Kart Live: Home Circuit experience outside and have Mario zip around on more solid surfaces like driveways, decks, and so on. That said, we really, REALLY recommend against it. The karts aren't built for outside use, and any dirt, moisture, or mud that get into/on the kart can permanently damage them.

We strongly suggest you follow Nintendo's guidelines and keep the action indoors. You'll ensure the longevity of your kart that way, making sure it's around and playable for years to come