The first part (could America conquer the world) would be much easier than the second part (if all the citizens of the USA were on board.)
If the attack on Pearl Harbor happened today, about ten percent of the citizenry would protest that the US Pacific Fleet wanted to use too much fossil fuel to counter-attack, there'd be a lot of debate about whether it was really a war over the oil in the Dutch East Indies, for many there'd be concerns that Privileged White Males were using the attack as an excuse to further the oppression of the Asian race, there'd be editorials about how the American presence in Hawaii was an immoral expression of imperialism in the first place, and Doolittle's Raid would have to be postponed for six months or so until a female pilot could be taught to take off from the USS Hornet.