$text1 = "Thursday, December 19, 2019 10:10 AM 668 about_this_site.txt"
$text2 = "December 19, 2019 10:10 AM 668 about_this_site.txt"
$text3 = "19 December 2019 10:10 AM 668 about_this_site.txt"
$text4 = "2019-09-19 10:10 AM 668 about_this_site.txt"
$text5 = "2019/09/19 10:10 AM 668 about_this_site.txt"

ConsoleWrite(_HasUSDate($text1) & @CRLF)
ConsoleWrite(_HasUSDate($text2) & @CRLF)
ConsoleWrite(_HasUSDate($text3) & @CRLF)
ConsoleWrite(_HasUSDate($text4) & @CRLF)
ConsoleWrite(_HasUSDate($text5) & @CRLF)

Func _HasUSDate($s)
    Local Static $aUSDate[][2] = [ _
    ["full_1","^\w+, \w+ \d{2}, \d{4}"], _ ; Tuesday, September 22, 2020
    ["full_2","^\w+, \d{2} \w+ \d{4}"], _  ; Tuesday, 22 September 2020
    ["long_1","^\w+ \d{2}, \d{4}"], _      ; September 22, 2020
    ["long_2","^\d{2} \w+ \d{4}"], _       ; 22 September 2020
    ["short_1","^\d{4}/\d{2}/\d{2}"], _    ; 2020/09/22
    ["short_2","^\d{2}/\d{2}/\d{4}"], _    ; 09/22/2020
    ["short_3","^\d{4}-\d{2}-\d{2}"]]      ; 2020-09-22
    For $i = 0 To UBound($aUSDate) -1
        If StringRegExp($s, $aUSDate[$i][1]) Then Return $aUSDate[$i][0]
    Next
    Return ""
EndFunc