If the popular uprising in Egypt gave Washington a real headache, the brutal crackdown on protesters in Bahrain involves even more complicated calculations for the Obama administration.
The US has condemned the use of violence against protesters in Manama but it has chosen its words very carefully so far.
On Thursday, Secretary of State Hillary Clinton said: "Bahrain is a friend and an ally and has been for many years and while all governments have a responsibility to provide citizens with security and stability, we call [for] restraint.''
President Barack Obama on Friday again spoke of universal rights, including the right to freedom of assembly, but American national interests hang in the balance, perhaps even more so than with Egypt.
Hosni Mubarak had been a US ally for the last 30 years.
Despite overseeing a repressive regime at home, he was seen by the US as a moderate president of a country with a peace treaty with Israel and a key partner in the peace process. But with the loud, overwhelming demand from the streets of Cairo for Mr Mubarak's departure, it became untenable to continue supporting him while professing to support those universal rights, so Washington took a gamble.
It came to the conclusion it could let go of a president who had failed to implement reforms because the Egyptian army, underwritten by the US, would probably maintain the country on a moderate path that would be mostly acceptable to Washington and, by extension, Israel, at least in the short term.
But when the US looks at Bahrain, it sees Iran and the picture blurs. Tehran and Washington have been foes since 1979 and Sunni kingdoms like Bahrain, but also its bigger neighbour Saudi Arabia, a vital US ally, are a crucial counterweight to Iran's growing influence in the region.
Tight-lipped in Washington
Bahrain is home to the US Navy's 5th fleet and is a key pillar for US regional military infrastructure.
Iran's nuclear programme is a key concern for the US, for Israel and also for the Sunni monarchies. Tehran's regional influence has been growing and the Supreme Leader, Ayatollah Ali Khamenei, has seized on events in Egypt as an Islamic awakening and the end of American hegemony in the region.
Bahrain itself, with its large Shia population, has its own specific fears of Iran. In 1981, the Iranian-backed Islamic Front for the Liberation of Bahrain attempted a coup in the country. Bahrain is linked by a causeway to Saudi Arabia, specifically its Shia-dominated and oil-rich Eastern province.
Bahrain's Shia have long been discriminated against in the country and they say their protests have nothing to do with Iran and everything with wanting to be accepted as full Bahraini citizens. They accuse the authorities of waving the spectre of Iran to stop the West from supporting them.
It may well be working for now. When hundreds of thousands of people took the streets in Egypt, many American officials, briefly forgetful of the complications this presented for their foreign policy, were glued to their television sets and some sounded ever so slightly excited at the sight of people power in action in the Arab world on such a scale.
There is none of that enthusiasm about the unfolding events in Manama. The violence of the security forces has shocked many and the sectarian undertones, real or imagined, mean everybody is more careful about the positions they take in public.
American officials have been very tight-lipped about their conversations with Arab rulers, only emphasising in public the need for real reform, repeatedly. It is an attempt by Washington to try to avoid having to choose again between an Arab leader and his people.