Everyone is afraid of tungsten 'Rods from God' but any nation capable of landing on an asteroid or Comet is also capable of turning it into a 'Sledgehammer from God' with minor alterations to its orbit. When it comes to solar objects that intersect Earth's orbit the value of an asteroid isn't it's precious elements but its mass.
Quite difficult to aim a massive asteroid.
You can have it hit earth, quite likely.
Have it hit an ocean, probably.
Have it hit within 1000 miles of the exact point you want? Very difficult.