Thankfully, NASA has already figured all this out, and that why DART was launched. John Q public and the various congress-critters are still catching up, and Hollywood has a lot to answer for, but the people actually defending the planet are on the ball.

Which is one of the reasons why Arecibo II will end up being built... it was the only deep space radio telescope that could also act as a deep space radar, and gave us a much wider window of detection.