Is there anyway to prevent people from outside the United States from registering?
This is always a difficult one to solve. So many people can fake an IP that you can hardly ever tell where someone is actually from. However, there are some ways to filter and Cloudflare would probably be your best option as they have a bit more advanced IP checking. They have free and paid versions. I use free on one of my sites. You can check to see if the IP filtering is available on the free plan and set it up so that only US ip addresses are able to reach your site.
Other than that, I don't know of a plugin to do it. Perhaps a user verification via SMS or something?
That's great thanks Donna! I'll check out cloudfare.
I have created the US block on cloud flare (although I can't test it). You really are the best Donna! xoxoxos
Cool! Hope it works for you and thank you!!