What I don't understand is why Americans portray themselves as Dutch when coming to the Netherlands.
Do they, though? Are there really that many Americans who think or try to pretend they are actually Dutch, instead of Americans who are have Dutch ancestry?
It honestly sounds like they are just trying to connect by sharing a commonality and something that is (probably) important to them in some way. It's an expression of appreciation. Even if the cultural traditions carried on in the US are different than in the modern-day country--so what? It doesnt make those cultural traditions less important to the people who celebrate them. I fail to understand what is wrong with acknowledging or appreciating where those traditions originated.
Is it just a matter of semantics and an objection to the label itself "(whatever nationality)-American"?
Right, and Irish-Americans have more knowledge and understanding about Irish-American culture.
The other poster was making it seem like American culture is homogenous or like descendants of immigrants can't still retain distinct cultural traditions and identities outside of generic American. Whether or not those traditions are the same as the original country of origin is immaterial. Nobody is claiming that it is.