'Pennsylvania Dutch' (i.e. German...) is a thing though, and a bunch of the Midwestern states preserve a lot of Germanic traditions, but as you say they mostly don't seem to have kept the hyphenated identity in the same way that (say) the Midwestern Scandinavian immigrants have.
The German American identity took a fair pounding during prohibition. German immigrants were obviously prominent in the beer industry and some prohibition campaigners used recent memory of WWI to try and make drinking associated with treason.
'Pennsylvania Dutch' (i.e. German...) is a thing though, and a bunch of the Midwestern states preserve a lot of Germanic traditions, but as you say they mostly don't seem to have kept the hyphenated identity in the same way that (say) the Midwestern Scandinavian immigrants have.