prejudice against Germans pre-WW I

Frankenstein, the book, was a story of science gone wild and, unlike the movie, was set in a centre of science and learning. The other great 19th century horror story, Dracula, was set in what is now Romania and in England, not Germany.

As for Germany, it was hardly backward and not considered so. It was a centre of European philosophy, education, science, and music. It didn't start to get a negative reputation in English speaking countries until the end of the 1800s when British and German foreign policies came into conflict.

I've heard anecdotes about Germans being viewed as one step behind the English and French, but victory in the Franco-Prussian War raised the status of unified Germany as an independent military power. Superior technology played a huge role, particularly the Krupp steel cannon.

In America, there were also hotbeds of pro-German sentiment among recent immigrants and their families, right up the entry of the US into WWI.

What I've gleaned from several WWI books and documentaries, is that Germany was the blustering bully that lived on your block (Europe) that was constantly stirring up trouble; you never knew what was bluster and bluff and what was sincere, especially during the reign of Wilhelm II.

You're going to have to do your own reading and draw your own conclusions if you want more than a superficial understanding of European attitudes toward Germany. Barbara Tuchman's "From a Dark Tower" is not a bad place to start, IMO.

I know in mid to late 1800s America German immigrants were considered beneath the native WASPs. However, they were not considered as bad as the Irish Catholics, Italians or Jews.

Have a look at the genre known as 'Invasion Literature' https://en.m.wikipedia.org/wiki/Invasion_literature which became popular in Britain following the Franco Prussian War.

Taking painting to the pictures ...
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