First split the stirng on '-' which will give you an array of strings between the dashes. Then use it as a stack and pop the last element off and call trim to remove any of that pesky whitespace (unless you like your whitespace of course).
"String - Location".split('-').pop().trim(); // "Location"
So using jQuery it would be
$('.v2_review-text').html().split('-').pop().trim(); // "United States"
Or using vanilla JS
var text = document.getElementsByClassName('v2_review-text')[0].innerHTML;
text.split('-').pop().trim(); // "United States"