The Yanks weren't exactly welcomed with open arms in Liverpool when the war was on.My recollection is they only got involved when they had to.
I cant speak to what the people of Liverpool thought of the "Yanks". But to say we "only got involved when we had to" is not entirely correct. In our Congress we had 2 sides. "Isolationist" and realist. The main argument against that war was it was "Europes problem". We lost a generation of our boys in WW1 fighting in war which was, lets be honest, started and controlled by Europes Royalty. Infighting between Europes Royal families that didnt send their sons into the trenches, but ordered the poor working classes to die for them to keep their monarchies. If you know anything about us we dont do well with Monarchies. That was still very fresh in the minds of our politicians. Many who fought in WW1 wanted us out of Europe. But by the early 20th century Britain was an ally. If your statement was true why did we decide to dedicate most of our efforts in Europe and not the Pacific? We retooled a massive amount of industrial production to war materials, to send too the British before Pearl Harbor.
Even after Pearl Harbor we didnt have to get involved. Japan wasn't capable of invading the US. Midway showed that. German had no way of invading us. They had no carriers or any naval threat that could force us to capitulate. They couldnt blockade us. Surround us or land any force.
So what was the reason as you stated that we "had to get involved"?
Even today its unlikely we could be invaded.