The reason the US does not sell weapons to China is purely political (the same reason they stopped selling weapons to Iraq). If American weapons manufacturers would be allowed to sell to China, they would do so in a heartbeat. So trying to make France and Germany out to be the bad guys is a little off the mark. The current political situation makes selling arms by US firms to China unacceptable. The current political situation for France and Germany is, understandably, quite different than that of the US (they are their own nations afterall; there is no "law" that all nations must do what the US does).
There's no great morality behind the US arms embargo. If there was, they would never have sold weapons to Iraq. Or any one of a number of military dictatorships in South/Central America. Or Iran for that matter.
Do you honestly think the US would foster a new world war over Taiwan? Yes, I know all the rhetoric, but do you think they really would go to war with China in this day and age? I don't. The support of the American people just isn't there. Especially after the Iraq fiasco. The only reason China hasn't gone in is b/c of the huge military disparity. As that gap closes, so too does the amount of time Taiwan remains independent, IMO.
All of this is moot, of course. China is on course to be the super power of the future, not the United States. And in that, one could call the actions of France and Germany forward thinking.