With the announcement of Niantic Wayfarer coming soon to Pokemon Go players, it is perceived eligible Pokemon Go players world wide will soon gain the ability to submit Pokestops, so this will finally not just be limited to certain countries.
Having recently worked with an Ingress player to submit POI ideas in my local area, I learned quite a bit about the process from him. I also learned how you can analyse the S2 cells in your area with tools such as IITC Mobile. This allows you to figure out where you need to make a submission and how many submissions you need to create another gym in a certain area for example.
At first glance apps like IITC Mobile might not appear to be the most user friendly, however once you have them setup correctly its very easy to use IITC Mobile to understand the area you wish to improve on Pokemon Go.
Learn more: Plan Pokestop Submissions In S2 L17 Cells With IITC Mobile.