I want the webform submitted report to be sortable (or filtered), suppose there is the "Country" field in the form with selectlist of Countries,
I must be able to filter the reports with specific value,suppose "USA" or something else.
You can do it easily with Webform Report module, using filters.
Install and configure the Webform Report module
Go to content > add new content > webform report
Select a webform which you want to extract a report of submissions
In "Report Criteria" section, select all the components (fields) from the webform that you want to display on your report.
select the fields you want to use to create a filter, In your case choose:
Type de filtre= equal, and Filter Value= USA