Both nations saw each other as potential and likely opponents early in the 20th Century, and more so after WW1.

It was a combination of several factors. Japan having gained Germany's former Pacific possessions, then Korea and Taiwan, and found herself with a budding Empire and wanting more, particularly the resource rich areas of China, Manchuria, and the East Indies.

Meanwhile the US had NO interest in giving up either her possession in the Philippines, Guam, Wake, or the Western principle of "Free Trade" in China.

Then several political factors caused a sharp rise in the feelings among the militants in Japan that the West was out to get them.

The first was the dissolution of the UK-Japanese alliance and treaties, without the Royal Navy backing Japan all of a sudden they found themselves left to their own devices. The UK saw Japan as a potential threat too and for multiple reasons drifted away from this new Imperial expansionist power eying Britain's far flung and valuable Pacific possessions.

Then in the Naval Treaties of the 20% Japan was forced to accept their bare minimum, and a 5:5:3 ratio for the RN;USN:IJN meaning that Japan would only have 60% of the tonnage of the US and UK, that led to common feelings that the Western Powers were afraid and out to get Japan.

Thus when Japan looked around to see who she would have to fight for dominance in the Pacific basin the US was the obvious foe and had demonstrated that she had little interest in giving up her status as dominant in the hemisphere.