Is it possible to fit an internal dropper to 2x bike I'm thinking about getting a XC bike and fitting a dropper. 

I've got my eyes on some of the cubes, ie 
https://www.cube.eu/uk/2017/hardtail/reaction/cube-reaction-gtc-2x-carbonnflashred-2017/

It's got a narrow seat post (27.2mm) and the only cheap dropper I can find to fit it needs to be internally routed. (http://www.chainreactioncycles.com/brand-x-ascend-27-2-cx-dropper-seatpost/rp-prod159175)

Is it going to be possible to internally route this , when the bike has a 2x not a 1x setup?
Being able to route an internal dropper is nothing to do with 1x/2x, and more to do with if the frame manufacturer has provided the facility to do so.  There will usually be a dedicated port in the seat tube.

As demonstrated by this Canyon Spectral (picture linked from Pinkbike):