Just two things to consider: A deflection attempt at scale would generate much more debris. And peppering the atmosphere with hundreds of 15kT impactors over the course of minutes will still heat most surfaces with line of sight to the event(s) above their flash point, because you have just optimized the conversion from kinetic to radiative thermal energy.
(I blame CGI for notoriously underselling the brightness of meteors)
Just two things to consider: A deflection attempt at scale would generate much more debris. And peppering the atmosphere with hundreds of 15kT impactors over the course of minutes will still heat most surfaces with line of sight to the event(s) above their flash point, because you have just optimized the conversion from kinetic to radiative thermal energy.
(I blame CGI for notoriously underselling the brightness of meteors)