The one that took out the dinosaurs was only a few kilometers in diameter IIRC. So, if a Texas sized asteroid hit it would probably split the earth in two. Which, some theorize, has happened before and is why we have a moon.
IIRC the theory is that it was a Mars-sized planet that hit ancient Earth, at a grazing angle apparently, and complete with an iron core (which mostly remained with Earth's to form the new Earth). A significant portion of the overlying mantle of both the impacter and Earth was ejected into space however, with a lot of it being captured by the Earth's gravity to form a ring around the Earth. Eventually the ring coalesced into the Moon, which probably was quite a spectacular object, glowing a ruddy red from the heat and appearing something like 20x its current angular size (10 degrees vs. 0.5 degrees). Also IIRC the new Earth's day was something like 5 hours long, having been sped up considerably by the grazing impact.
Being so close to the new Earth, the Moon must have raised large tides once the Earth's oceans formed, slowing down Earth's rotation (which angular energy was transferred to the Moon, causing it to move out to its current orbit). The Moon's orbit continues to move further out by about 4 centimeters per year IIRC, but the rate is slowing down as the transfer of angular momentum also slows down. Eventually the Moon will take something like 2 months to circle the Earth, but that's a billion years or so into the future.
Some theories hold that life originated in the tidal pools once oceans formed, so we can thank the Moon for our existence if true.