OK so at the end of the movie Newt defeats Grindelwald. However, Grindelwald was already in possession of the Elder Wand so shouldn't Newt be in possession of the wand thereby upsetting the timeline?

I think you only get the elder wand if you kill grindelwald

No. Snape killed Dumbledore, but he didn't get true possession of the wand because Draco had defeated Dumbledore first. Thus, Newt has to be defeated by Grindelwald or someone who gets defeated by Grindelwald for the timeline to be okay.

Yes, and no. Because I'm pretty sure this is before the final battle. I think grindelwald escapes, and then goes after Dumbledore, no older wanting to waste his time knowing how easily he could be captured. That's why he was getting close to the boy, because he wanted the power so he could kill Dumbledore. But now he knows he's not infallible, and he needs to go and fight Albus.
I can't remember if Newt disarmed him, I don't believe he did, so Grindelwald is still in possession of the elder wand. If he did, then Grindelwald will fight with Newt again, and disarm him, and make the elder wand his again.
Grindelwald wasn't defeated. He was captured. Those are two different things. A Nazi can be captured, but that didn't end WW2, Hitler was defeated.
And it isn't about defeating, its about disarming. Expellarmus. Harry disarmed Draco, he didn't defeat or kill him.

Does he even have the wand yet?

.... Good question. He knows about the Hallows, at least.

Did he use his wand to defeat Grindelwald? I only recall him using the Swooping Death to tie his limbs up.

The woman did something right after he restrained him (forgot her name)

What if, for whatever reason, the Elder Wand is in America? Of course, he may be in America simply to take over it, but if he isn't even completely finished in Europe, then there may be a different motive.

The elder wand was with that wand maker guy. He was russian. So no, id say its not in America.

But why is grindelwald in America

He wanted the power of the Obscurus.

Surely it wouldn't be too hard to find one closer to home?

They were described as incredibly rare, which is probably why he legged it all the way to America looking for it. Plus he was on the run, couldn't hang around the usual haunts unless he wanted to get caught.

(Can i just say I'm loving this discussion :D)

Gregorovitch might be hiding it, but probably not.