Reduced width when importing .ai file to After Effects

[Pascal5D73]

I created an illustration with the dimensions 15360x8460 (=4*4K).
To do animations, I save it as an .ai file and import it into After Effects.
For some reason, the dimensions of the .ai file in After Effects turn to 14400x8640, aka the width is reduced.
This doesn't happen when I export the illustration as .eps instead of .ai, why is that?
However, I'd like to use the .ai file in After Effects. 
What do I have to do so that the dimensions are correct?

[Mike_Gondek]

Does the artwork look  stretched in one direction? Do you have any stray elements soutisde that artboard.

Try copying your art and pasting into a new document set and set the document Raster Effects at 72 ppi.

https://community.adobe.com/t5/after-effects-discussions/illustrator-file-dimensions-change-when-imp...

[Pascal5D73]

Thanks for the reply!
It doesn't look stretched, it just doesn't fit the entire width of my AE composition. 

Here in AE it says 14400x8640:

while in Illustrator it is 15360x8460 (see ruler) as it should be:

The weird thing is that when I save the Illustrator Project as an .eps file, the dimensions are correct when I import it to After Effects. The width cut from 15360px to 14400px only happens to the .ai file.

[Pascal5D73]

btw, Raster Effects were already set to 72ppi

[Ton Frederiks]

Check the pixel aspect ratio in Illustrator (in the Artboard Options) and in your After Effects composition.

[Pascal5D73]

In AE it's set to Square Pixels.
Do I have to set it to Square Pixels in Illustrator too?
How do I do that?
In the Artboard Options there's only "Video Ruler Pixel Aspect Ratio", 
and I have to insert a number there.

[Ton Frederiks]

Try 1 for Video Ruler Pixel Aspect Ratio. I am not sure if After Effects reads this, but it could explain the distortion if it is set to something else than 1.

[Pascal5D73]

Oh there is actually no distortion of the illustration at all if we talk about stretched image or something like that.
The illustration is LITERALLY cut off. 
In the pictures that I attached in another reply above you can see that New Zealand is completely cut off in After Effects, while being there in Illustrator.

It all looks as if After Effects can't import an illustration with a width of more than 14400px

[Ton Frederiks]

If you base your artwork on a Video & Film preset there will be 2 artboards.

With a single artboard, After Effects clips the content outside the artboard even when Retain Layer Sizes is selected.

With the second large artboard, AE will show the contents of layers when Retain Layer Sizes is selected.