That’s a tricky question, because the USA successfully halted Japan’s actions in China with an embargo on steel and oil.
Which lead to the Japanese attack on Pearl Harbor, in an attempt to destroy the US fleet and lift the embargo.
Only then did the USA declare war on Japan, but they didn’t do so in order to help the Chinese.
They did it because of Pearl Harbor, and because their own dominance in the Pacific was threatened.
That’s a tricky question, because the USA successfully halted Japan’s actions in China with an embargo on steel and oil.
Which lead to the Japanese attack on Pearl Harbor, in an attempt to destroy the US fleet and lift the embargo.
Only then did the USA declare war on Japan, but they didn’t do so in order to help the Chinese.
They did it because of Pearl Harbor, and because their own dominance in the Pacific was threatened.