As I understand it, since the Nile River flows North to South, did the Egyptians think the world was upside down to what we know it is? I'm not sure how much of Egypt and past it they knew of back in say the old or middle kingdoms, but didn't they think the the world was upside down? I look at maps of of Ancient Egypt and was curious, though all I found were right side up.
Your premise is somewhat flawed. Rivers don't flow according to magnetic fields, they flow according to gravity (i.e. downhill). The Nile flows (largely) from Lake Victoria in the Rift Valley down to the Mediterranean a drop in elevation of some 9000 feet (for the White Nile tributary) over its 4000+ mile length.
To expand your question into why north is up on maps, there are a number of posts in the wiki regarding maps in Egypt and North/South orientation.
I look at maps of of Ancient Egypt and was curious, though all I found were right side up.
Just wanted to add a comment that it doesn't appear that any maps have been found that were created by Ancient Egyptians. A couple of threads may be of interest
Are there any surviving maps of Ancient Egyptian cities? As in, maps made at that time? featuring /u/Kylarnatia and /u/kookingpot
Did the egyptians have any sort of mapping system featuring /u/MarcEcko