Of course, the Japanese could have chosen to get the materials peacefully.
but the real problem remained the army in china, and the inability of either the Navy or the civilian government to control the army much. the army was paralyzed by what they called “debt to the dead” meaning by that time they had lost 200,000 troops and couldn't pull out with nothing just because the US said so. so the US presented a basically unsolvable problem to the Japanese, pull out of china, which they couldn't do, or shut down the country in two years or less for lack of oil and materials.
its for this reason i have to feel that the US was a party to the drive to war, and that war was the predictable outcome.
Certainly, but that was more a product of the fact that this is where Japanese aggression was centered initially than being about China itself. When Japan made moves on China in the late 1800s, the U.S. was less interested in it than they would be once Japan really became a legitimate power in the region.
You do not see much of an American response when the assassination of Kim Ok-kyun along with the Tonghak Insurrection triggered the Sino-Japanese War in 1894. This fight against the Qing would lead to the Japanese taking over the Korean peninsula along with a chunk of Manchuria (the Manchurian district would be given back after the war at the behest of the French, Germans and Russians). The United States only response to any of this was to declare the "Open Door" policy in 1898.
Even when the Japanese invaded Manchuria in 1931, there was not much of an American response. It wasn't until the Japanese expansion began to pose a threat to western European ligations that the U.S. started to take an interest in Japanese aggression in China. Up until Lend-Lease started supplying the Chinese, the Soviets were the largest suppliers of arms and advisers to the Nationalists (this started to dry up in late 1939 and disappeared completely once Germany invaded the Soviet Union).
I'm not saying that the U.S. didn't support the Nationalist's cause, but I can't say that Jiang Jieshi was the primary reason the U.S. began to oppose Japanese expansionism in the Pacific.