^(\+\d{1,2}\s)?\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$
Matches the following
123-456-7890
(123) 456-7890
123 456 7890
123.456.7890
+91 (123) 456-7890
If you do not want a match on non-US numbers use
^(\+0?1\s)?\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$
Update :
As noticed by user Simon Weaver below, if you are also interested in matching on unformatted numbers just make the separator character class optional as [\s.-]?
^(\+\d{1,2}\s)?\(?\d{3}\)?[\s.-]?\d{3}[\s.-]?\d{4}$