Upvote:2
There were enough concerns about the United States and Germany that the Tariff Reform League was established in 1903. But according to sources attached to its Wikipedia page, it never had more than a quarter million nembers, and seems to have been instrumental in the Conservatives losing the 1906 election (due to party division).
While the League dissolved in WWI, the Conservatives ran with an outright protectionist argument in 1923, and again lost.
Even voluntary programs like the Empire Marketing Board failed.
It wasn't until 1932, in response to the Great Depression, that major protectionist legislation was passed, simultaneously with the dominions, to create an empire-wide tariff scheme known as "imperial preference".
So, I think it can be safely said that the public were ambivalent to hostile towards protectionism generally; but their attitudes towards American or German products specifically is harder to source (although, post-WWI, it's easy to guess their opinion on German goods). And it doesn't look like there were any non-reciprocal tariffs targeting them specifically.
I hope I haven't gone over everything you've researched already.
https://en.m.wikipedia.org/wiki/Tariff_Reform_League https://en.m.wikipedia.org/wiki/Empire_Marketing_Board https://en.m.wikipedia.org/wiki/1906_United_Kingdom_general_election https://en.m.wikipedia.org/wiki/1923_United_Kingdom_general_election https://en.m.wikipedia.org/wiki/Imperial_Preference
Upvote:5
We could start with Wikipeda
"The most notable sign of improving relations during the Great Rapprochement was Britain's actions during the SpanishβAmerican War (started 1898). Initially Britain supported the Spanish Empire and its colonial rule over Cuba, since the perceived threat of American occupation and a territorial acquisition of Cuba by the United States might harm British trade and commercial interests within its own imperial possessions in the West Indies. " The Great Rapprochment
Or another summary
Britain persisted in its free trade policy even as its major rivals, the US and Germany, turned to high tariffs (as did Canada). American heavy industry grew faster than Britain, and by the 1890s was crowding British machinery and other products out of the world market.[57] London, however, remained the world's financial center, even as much of its investment was directed toward American railways. The Americans remained far behind the British in international shipping and insurance.[58]
The American economic "invasion" of the British home market demanded a response.[59] Tariffs, although increasingly under consideration, were not imposed until the 1930s. Therefore, British businessmen were obliged to lose their market or else rethink and modernise their operations. The boot and shoe industry faced increasing imports of American footwear; Americans took over the market for shoe machinery. British companies realised they had to meet the competition so they re-examined their traditional methods of work, labour utilisation, and industrial relations, and to rethink how to market footwear in terms of the demand for fashion.[60] Free Trade
If you want to dig further, I would suggest consulting the references linked in the above articles.