I’m assuming that you have a “tileable” texture; the texture can “wrap around” on a 2D plane without showing seams, and that this issue arises from two separate world objects (which is kind of suggested in your question).
You might want to look into using Absolute World Position based UVs. This makes it so the UVs that your textures use aren’t mapped from their position locally on a specific object, but are based on where the object’s vertex exists in world space.
You do this my changing your material setup so that the UVs for the texture are taken from an “Absolute World Position” node (kind of self explanatory I guess, once you know the jargon 
) Anyway, (bom, bom, bom) has a little tutorial on how to achieve this:
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NB. Do note, if you have any steep angles up the Z axis (cliffs etc) you might see some nasty artefacts owing to UV stretching; there are ways around this too - however if I’ve understood you correctly, this should be what you’re looking for to get over the main hurdle.
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