What would have happened if an Asteroid the size of the state of texas would have struck the earth back in 1978?

2  leggers a gone species

Well if it hit at 50,000 mph there would be major damage but if it hit at a subsonic speed everything would be ok

Most of the weak life would vanish, with no chances to repeat itself. Only the strongest forms would go on. 'Some' experienced similar on Earth, with no such intensity but they go on as modified.

It would've caused a mass extinction.

Well, consider that one just 6 miles in diameter wiped out 90% of the land species on Earth 65 million years ago... if an asteroid 100 times larger hit - pretty much, that would’ve wiped out most - if not all - life on Earth... 1978 would’ve been the last year of mankind. 

There would be no internet for sure, no earth either.

You wouldn't be here asking this.

Neither Jesus or Noah's ark would be able to save a damn thing. 

Depends on the relative speed between asteroid and Earth.  If it is typical 40,000 mph, then the blast would be equal to a few dozen quadrillion large H-bombs, leaving a hole about 10X the size of Texas or 7000 miles wide.  That would cover most of a hemisphere.  It would be about 2000 miles deep.  

The opposite side of the Earth would be fractured and covered in lava a few dozen miles deep.  If there was any atmosphere left, it would be very thin.  Surface water would be boiled away.  Orbit of the Earth would be changed.  It would be either farther from the sun or closer, or very oval, leading to long winters and very short, scorching summers.  Perhaps later Earth would collide with Jupiter or be ejected from the solar system.

Not a very nice day, especially for any survivors.

It would have blown Earth to Pieces

…… Maybe the Pieces would survive