What region and server to choice for Nvidia Enterprise for a organization

Choice of region and server really depend on what you are trying to achieve as use case.

Without this info, you can look here: https://aws.amazon.com/nvidia/ where Px or Gx ec2 instance could be a starting point.

As region there are implications about latency, service availability and more. From my experience, Ireland and Frankfurt are typically the most complete where features get sooner to be released, but as said, you ll need to look at your requirenents and then pick up one.