Set the Instant Pot to Saute, and add meat to inner pot. Saute until the meat, for about 6-8 minutes, until cooked through and browned. If there is more than 1 tbsp of grease, drain the meat.
Add 1 cup of water to the Instant Pot, and scrape the bottom of the pot to loosen any browned bits, or fond.
In order, add the following ingredients to the Instant Pot: taco seasoning, corn, beans, boxed macaroni (pasta only), remaining 1 cup water, and salsa. Do not stir.
Close the Instant Pot with the lid, and set the Instant Pot valve to the “sealing” position. Set the pressure cooking (or manual) setting for 5 minutes on high.
Allow the pressure to naturally release for 5 minutes. Then, turn the Instant Pot valve to "venting" to manually release any remaining pressure.
Add the cheese packet (from the macaroni and cheese) and sour cream to the pot, and stir to combine.
Portion the Instant Pot Tex-Mex Macaroni and Cheese into serving bowls. If desired, top with additional sour cream and fresh vegetables*. Serve and enjoy!