the US, between 1880-1910, was also experiencing a massive influx of immigrants from Europe, especially Ireland, England and Germany.

there were massive 1mill+ german and british communities who still had ties to their native homeland and consumed a lot of german speaking or English newspapers so there wasn't an overwhelming public view of either side. the irish largely favoured Germany due to britains colonialist ambitions in Ireland.

In 1914, a british ship, the teleconia, deliberately cut germany’s underwater communication cables, eliminating germany’s principal means of contacting the outside world. Now, with only a weaker wireless radio system left to send messages, British cryptanalysts could easily intercept and decipher German messages.

Soon after the cable cutting, british parliament passed the Defense of the Realm Act, which gave british censors the ability to dissect modify news and opinions traveling to the United States via Britain (which was the majority, given their geography)

from then on during ww1, Britain had dominance in underwater sea cable control.

With an effective propaganda machine, and tight control over news from Europe (stopping german propaganda from ever reaching the german american public) to the United States, Britain was able to influence American public and governmental opinion, thus nurturing a pro-Ally and anti-German stance in the United States.

edit; im on the my phone and i just realised I completely wasted time by answering it on ww1 and not ww2