How and where did the USA fight Japanese first in WW2?

Question:

how progressed after and why?

Answer:

The Japanese came into conflict with the United States over the `Panay ` incident in 1938 , in December of that year Japanese aircraft and artillery sank the American gunboat Panay and damaged the British gunboat Ladybird .
United States sailors obeyed orders to abandon the Panay , the small craft which rescued them was afterwards machined gunned. The US did not respond with military action but increased their support of Nationalist China with arms and money.