Considering the World War 2 we know that USA didn't even bother entering the war for more than 3 years and they only got into it when US mainland was threatened (the Pearl Harbor thing). There is no reason to think they'd do anything different today either.
You should also consider that 2024 is not 1940's, during the 40's it was near impossible to effectively reach the US mainland. However in this day and age reaching US mainland is a piece of cake which means if they enter any kind of armed conflict, unlike WW2 the US mainland will be completely destroyed similar to what happened to Europe and elsewhere during WW2 and worse.