Are mining pool managers evenly distributed across the planet? where are the biggest ones located? Like where are the servers physically located? Recently the backbone ISP for all of the Universities in Michigan went down and everyone on each campus was offline1. Could something larger of this nature potentially take out some pool managers and therefore some pools, thereby increasing the hash share of the online pools and risking a 51% attack?
Evenly distributed, no.
There are pools on nearly every continent.
But a pool only has the hashing power of the individual miners participating. Miners can (and do) jump from one pool to another when connectivity issues occur, or when workload isn't received, or when payouts stop.
Individual miners are much more spread out. Areas with cheaper electricity got higher participation than areas with lower electricity, but now with ASICs that will probably not be as much of a factor for a couple years again.