Hi Shyam,
Yes, you can restrict your website to only US region IP addresses. There are different potential methods you can use.
For example, you could put Azure Application Gateway in front of your VM and use Geomatch custom rules to limit to US.
Geomatch custom rules
https://learn.microsoft.com/en-us/azure/web-application-firewall/ag/geomatch-custom-rules
Another option would be to use third-party geo filtering extension/module/filter running within the VM. For example, if running IIS for the web server you could use a third-party IIS module that provides the geo filtering capability.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP