Are you using one giant image or something for your map?
If you are, the "map size" isn't the issue... it's the fact you're using one massive image to show it. Never, ever, ever.... ever use one giant image for things like that if you want it to run nicely on a lot of devices. For PC it's not so much of a problem because graphics cards these days have like 8gb of RAM and stuff like that, but it will kill a tablet or phone, or even an older desktop computer.
Break up your images into small tiles, or separate images to build your map from "pieces" - this will help a lot.
If you already have broken up the map graphics into several pieces - this could also be a problem if there are simply too many objects. A decent PC can handle a good 10,000 static objects without much problem, but I notice even 2,000 objects can slow down my phone. If this is the case, then you may need to make some way of only creating the map tiles/objects if they should exist on the screen at the time, and literally destroy/delete everything that's not visible to the player.
Have you got some example of how you are making your map? It will be helpful for a better suggestion to fix the issue.
~Sol