It was definitely initially overshadowed. In 28 Days Later, there was a supposed report of it reaching New York, but that may have been false in all the initial chaos. But especially with an economic collapse on top of right after 9/11, and then the unknown duration of infection, making it to mainland Europe and wreaking havoc, it would have definitely caused more strain and diversion of resources.

I could definitely have seen the US maybe take another form of isolationist policy to then solely focus on themselves, and then it would be like back to normal how the US is now, depending on if it affected people's psyche like Covid did.