meforkene:

Cersei, Dany and others would still exist but then there's no more a three-eyed raven as Bran hasn't trained anyone. So history of man and himself the NK would be gone.
Importantly, he believed he was going to clear the entire Winterfell where all that have heard about how he can be killed are at this point in time.
His only challenge would be the meisters and books in Old town which is a minor problem for him.
With his large and growing army he'll just conquer everywhere and Cersei...beat them with numbers.
If it's about swimming, that man would build ships (they make uniforms, armour, boots and even have big metal chain).

That's what I feel.

Thanks! This was a tad-bit helpful and insightful.

See the explanation I got from the net!
The Night King doesn't really care about Bran Stark, but he cares very much about The Three-Eyed Raven, which is the magical being Bran Stark has become.

According to Bran, who is all-knowing at this point, the Night King's real goal isn't just to rule Westeros, but to erase it. And, as Bran explains, "I am its memory." The "its" in question is the world.

Samwell Tarly backs this up, explaining that Bran's "memories don’t come from books. And your stories aren’t just stories. If I wanted to erase the world, I’d start with you."

There have been a number of larger theories about the Night King's enduring obsession with Bran/The Three-Eyed Raven over the years, but Bran settled the mystery directly tonight - S08E02. The Three-Eyed Raven is the keeper of the memories of man and the Night King wants to destroy all trace of mankind. As a result, he needs to take out The Three-Eyed Raven to complete his big picture plan.

So with this said Bros, it would have only been a matter of time for the NK to come for Cersei and Daenerys wherever the fvck they are if he had successfully killed Bran and we all know his army would have multiplied like viral cells and Cersei and Daenerys stood no chance as the NK is hell bent on wiping out the whole of human existence.

This is why I said Daenerys didn't just come to fight for the North or for the love of Jon but saw the bigger picture as Jon preached about defending the survival of mankind in the battle against the dead.
This further gives credence to the meeting with Cersei although Cersie declined joining the fight, but didn't matter anymore since the NK was killed without her assistance.

Thanks once again Bros! I hope chaps here will be reasonable enough to read and see Daenerys didn't just come to fight for the North, but for human survival with a larger force.