To make things worse, Israel's boarding of the Turkish Flotilla in international waters may be construed as a possible act of war under international law.(Yes, wars have started over boarding other nations ships and it can happen again). If this act of the Israeli's is held to indeed be an act of war by Turkey or the international community, that means that Israel preemptively attacked a NATO ally's ship which could in theory invoke the mutual defense clause of the Treaty against Israel. I doubt that the powers that be would allow such a thing to happen, but if the NATO says it won't defend Turkey, then Turkey could accuse NATO of acting in bad faith and pull out of NATO as a sham organization. This could seriously cripple many strategic assets of the US in the Middle East and significantly alter the regional balance of power. (Lets not forget the US Nuclear missiles based in Turkey.)
The US is not in a position to sustain another major war, we have squandered our money on banker bailouts, bogus health care takeovers, and the last two conflicts in Afghanistan and Iraq have had a huge price tag as well. Israel's attacking a Turkish warship could cause a major conflict, and the US is ill prepared to engage in another major war at this point. A major war at this point could completely financially destroy the US. Our money is too little, our troops are spread too thin, and our political leaders are totally inept. If the Turks don't back down from this Israeli warning there are stormy seas ahead. If they do back down they're could be internal political problems in Turkey and a loss of face abroad. (Lets not also forget that conflict on the Korean Peninsula could break out at any moment as well, so that would raise the risk of a major two front war. and yes the Chinese and the Russians would probably get involved and probably not on our side.)
Land wars far from home with complex lines of supply through the Middle East, perhaps not. However the US is certainly in a position to win a large number of simultaneous sea-air wars.
The Chinese would be fools to attack us. Economically, we are their manufacturing bread and butter - not to mention that they hold massive amounts of our debt instruments.