Don't underestimate the bloody thirst of America evangelicals to kill Muslims anywhere, USA never give a damn about UN security council or UN resolution when it comes to Israel, the lobby that control US will push for US military support to save Israel, there is no doubt this attack has scared the Jesus out of Israeli's, and now their indiscriminate bombing is prove that they are humiliated. As for Egyptians joining the war I think you will be disappointed, I don't think Egyptians will do anything beyond providing Ambulances and medical aid but fighting Israel directly is not happening.