The overall consuming emissions contribution of the transport sector is at around 20%. The building sector (hvac) seems to be similar.
Cars are not efficient machines. The engine is limited to around 50% efficiency, the heat is wasted. And you're typically propelling 1600+kg of mass which is almost purely overhead.
Heating and cooling trumps the transport sector with 30%+. Globally, stuff does skew a lot from our first worldly habits.
If you do the calculations similar to those done in http://withouthotair.com/ you'd see your first worldly habits put your heating and cooling at the top, and probably your diet at the second place.
Energy use is not the same as CO2 production. Cars produce a lot of CO2 in the oil extraction, transport, and refining stages. Heating and AC use wind, solar, electric, nuclear, etc not just fossil fuels.
Cars are not efficient machines. The engine is limited to around 50% efficiency, the heat is wasted. And you're typically propelling 1600+kg of mass which is almost purely overhead.