The US was very vocal against Japanese aggression in China in the 1930's and early 1940's but said nothing against German aggression in Europe. The US finally placed an embargo on sending oil and iron ore to Japan as a protest but did nothing against Germany. Yet it would seem that China at that time was not a vital interest of the US but Europe, with friendly nations like England and France, was. The embargo finally caused Japan to look for other sources of these vital materials which eventually led to the attack on Pearl Harbor. We declared war on Japan as a result but not on Germany. My question is why did we put up with Germany's actions but not Japan's? I know that we aided England with Lend Lease and such, but we maintained diplomatic relations with Germany and did not protest their actions the way we did with Japan.
There was considerable political opposition to the US becoming involved in European affairs again. Perhaps the most influential of these was Charles Lindbergh and the America First organization he was affiliated with. When you read through his speeches and other non-interventionist, you'll see that their main focus was on Europe. These groups fell silent for the most part after the German declaration of war against the US following Pearl Harbor.
There was less concern about Japan in the general public. For the most part, up until Pearl Harbor, people didn't think an Asian power would pose a threat. They considered the aggressive, yet diplomatic, moves to be sufficient to curb Japanese aggression in Asia. It wasn't seen as a prelude to war as much as things like Lend-Lease and proposed arms sales to Britain were.
As I noted above, Lindbergh's and America First's opinions were the predominate ones when it came to non-interventionism in Europe.
From America First on the Charles Lindbergh site:
The above principles expressed the general thoughts of the movement. The attack on Pearl Harbor shattered the first 2 points, weakened the 3rd and made the last one moot.
Before that attack followed by the German declaration of war, with the memory of WWI and its aftermath still fresh in the minds of middle age and older Americans, many did not want to become entangled in what they saw as another European war. Most were concerned about the rise of Germany as a power in Europe again although there was much division about the way to deal with it. Lindbergh's idea of "impregnable defense" competed with FDR's limited interventionism.
Polling data from the era isn't as accurate as today's polls but they indicated that about 2/3's of the public supported FDR's policies but that America First was gaining support quickly in some regions of the country, enough that the 1942 mid-terms could have caused a switch in opinions in Congress.
Germany was not a DIRECT threat to the United States. There were two reasons. First, Germany had no navy to speak of (unless it captured the British fleet). Second, the U.S. was counting on Britain and France to contain Germany (until May/June 1940).
Japan was a much clearer threat to the United States. First, because there was no counterweight in Asia to Japan. Second, Japan had a real navy, one that actually more powerful than that of the United States BEFORE Pearl Harbor. That disaster was a consequence, not a cause, of U.S. naval inferiority. (Japan overbuilt, and the U.S. underbuilt the 3-5 ratio prescribed by the Washington Naval Treaty.)
If the United States had been able to defend Britain against Germany, it needed only to defeat Japan in order to be "safe." The combined U.S. and British fleets would have deterred an invasion across the Atlantic. On the other hand, an Axis victory scenario would probably have involved a Japanese fleet convoying a victorious German army from Siberia across the Pacific to Alaska and British Columbia.