Lets do the math. We will assume that 100% individuals switched to electric cars and heat.

Commercial and Residential Sector Emissions for US - 12% All Transportation for US - 29% (It includes rail and aircraft. Only 60% of it is light duty vehicle and I couldnt find what percentage of it is commercial transport)

So we have 12%+ 29%0,6 = 32%. It is big number but now we have to produce same amount of energy in electricity. 79% of all electricity generation was fossil fuels.

32% (0.21) = 7%

So even if all individuals will stop using fossil fuels for heat and will use electric cars for transportation. We will have less than 10% of reduction.