could we develop a giant city sized laser to melt asteroids?

Could we make a system of “satellites” that circle the earth from the distance of say saturn or neptune that could make a circle of detectors for asteroids headed towards us? Say using some echo waves to one another and if it hits an asteroid we’d notice from the echo levels or something like radio waves or something?

Why can’t we have AI monitoring the sky also on earth or with that satellite system also? Not developed or impossible to do so? from what I saw it’s just seeing the night sky suddenly changing with one dot and our vision is limited to facing away from the sun to spot them