There's a poem written by a Dutch-American during the war. I forgot how it went, but it ended with 'Op voor het Tweede Vaderland!', which means as much as 'Up for the Second Fatherland!'
Dutch immigrants saw, like many Germans and other immigrants, the USA as their new fatherland and wanted to fight for it. Them there are the obvious boredom/adventure reasons.
That being said, the Dutch contribution was small, alltrough we don't know the exact number. There certainly were thousands of soldiers with Dutch blood, but there's always the question when exactly someone stops being a Dutchman and becomes an American. Dutch immigration was centered around west-Michigan, by the way.
