Despite Mubarak being a strong ally of the US that has propped him up for three decades with money and weapons, there are no indications that the US government is planning to intervene militarily to support him. That is a good sign. It is annoying to hear the US government tell the people of Egypt what it would like to see happen there but that kind of patronizing interference is the norm these days and is on the scale of things a minor irritation. (You can imagine the outrage if the roles were reversed and the leader of some other country presumed to lecture the American people on what kind of government they should put in place.)
What is interesting to observe is to what extent these mass uprisings will spread to other countries. The president of Yemen, in response to planned protests against his three-decades long rule, has already said that he will not run for re-election in 2013 and will not pass on the leadership to his son. This practice of creating hereditary dictatorships is reprehensible and this move is to be welcomed though it is not clear if it will satisfy the anti-government demonstrators.
Meanwhile Jordan’s king has fired his cabinet in response to protests there.
But these are relatively unimportant countries from the point of view of US strategic interests. The real question is Saudi Arabia. If that long-time, oil-rich ally of the US, the key to its middle eastern strategy, becomes destabilized and its despotic regime of dynastic rulers is threatened, there is a real danger that the US will be tempted to prop it up militarily or support a pro-US military coup.