Very much so, if only because the words Yankee, dollar, Santa Claus, cookie, coleslaw and snack are derived from the Dutch "Jan Kees", "daalder", "Sinterklaas", "koekje", "koolsla" and "snakken" :)!
More: http://en.wikipedia.org/wiki/List_of_English_words_of_Dutch_origin
But no, the Pennsylvania Dutch are not of Dutch but of German origin..