Attacks on US embassies in Benghazi, Cairo and Sanaa should not be allowed to undermine support for change in the Arab world. How the young governments in these countries respond to the attacks will be a major test. The immediate response has been mixed.

The Libyan government has been quick to condemn the attacks and promised to bring those responsible to justice. There also seems to be a broad objection to the attacks by most Libyans. The assault is a clear illustration of the state’s inability to impose a monopoly on force.

The same cannot be said of Egypt, which has a long-established and effective security apparatus. While the assault on the embassy in Cairo was less damaging, the response from the new Muslim Brotherhood has been conspicuous by its absence, at least initially. The government of President Mohammad Morsi, which only came to power in June, appears more concerned with its own domestic appeal than with US anger over the attack. It has since toughened its stance, pledging to protect foreigners and condemning the killing of the US diplomats in Libya.

But this will do little to address the suspicions, held by many, both within Egypt and beyond, over the ultimate intentions of the Muslim Brotherhood. It may well have a lasting effect on the nature of future US support for Morsi’s administration. In the current environment, it will be much harder for Obama to back the country, especially with his own political fate hanging in the balance.