Unless a massive conversion to nuclear happens, it is not yet near possible to power everything with alternative energy sources; and so at this time, cheap natural gas crowds out coal and/or oil with about half the carbon emissions of those sources
Please to browse the charts and graphs at this page - and keep in mind that renewables they mention are not entirely carbon-free (it's complicated)
https://www.eia.gov/energyexplained/us-energy-facts/