Most historians agree that the attack on Perl Harbor was motivated more by the success of Admiral Togo at Tsushima when he destroyed virtually the entire Russian Baltic Fleet with only trivial losses (three torpedo boats) of his own. While Russia was capiable of continuing the war with Japan, their more pressing concerns in Europe prevented them from committing more troops to the war, and consiquently Russia sued for peace and the two nations signed the Portsmouth Treaty.

Using that as a basis for their planning, it is generally agreed that the Japanese high command was worried about the US intervening in their expansion into China, the Pacific, and eventually Siberia. Thus, the attack on Perl Harbor was seen from the Japanese POV as a warning shot, a message to the USA to keep its nose out of Japanese affairs, and was inspired not by failure against the Russians, but by the earlier success against the Russians.

Obviously one cannot say that Japan’s action were not wholly unmotivated by Khalkhin-Gol, most historians do not think it was a particularly formative moment in Japan’s military history. Especially when the Japanese Imperial Army had been aggitating for an expansion into China, not Russia, for decades.