The term asteroid was used for the TV movie appropriately called "Asteroid" (1997).Both the Bruce Willis movie "Armageddon" (1998) and the earlier, critically-panned "Meteor" (1970) used the term meteor(technically meteoroid) but both objects were asteroid-sized.The Tea Leoni movie "Deep Impact" (1998), and the TV movie "A Fire in The Sky" (Richard Crenna, 1978) had comets hitting the Earth.
The movie you're referring to is "Armageddon" (1998), which follows a group of deep-core drillers sent to space to plant a nuclear bomb on an asteroid the size of Texas that's on a collision course with Earth.
Because it was headed towards earth. It was bound to happen.
There is no way to avoid an impending collision.
the asteroid raced across from Mars to Jupiter
There are no known asteroids the size of Texas that have even the slightest chance of hitting Earth. The only known Texas-sized asteroid is Ceres, which has a stable orbit in the asteroid belt and could never hit Earth.
Armageddon
You cannot "avoid" a collision; if the asteroid is headed this way, it will hit. They aren't steerable. Give us another 50 years or so, and perhaps we would be able to prevent it.
No, an asteroid cannot destroy earth, but a large enough asteroid can have devastating effects on the life on Earth
No, if the Earth was destroyed by an asteroid we would not be living today.
Yes, the asteroid belt starts properly after the orbit of Mars.
Yes, if the asteroid is captured by the Earth's gravitational pull.