That's becoming the conventional wisdom, but I don't see how it's necessarily true. Yes, as many reporters have become aware of in the last few hours, the updated (2006) Foreign Operations, Export Financing, and Related Programs Appropriations Act says this of coups:
None of the funds appropriated or otherwise made available pursuant to this Act shall be obligated or expended to finance directly any assistance to the government of any country whose duly elected head of government is deposed by military coup or decree.
Sounds like Egypt, where the military gave Mohamed Morsi a deadline to resign, and then informed everyone that he was out, despite his loud disagreement. In order for our government to deny that this was a coup, we need to ... just sort of ignore that it was a coup. That's what we did in Haiti in 2004, that's what we did in Honduras in 2009, that's kind of what we did in 2011 when the military kindly accepted Hosni Mubarak's resignation. Mubarak was an autocrat, yes, but for three decades he ran in (un-loseable) elections against limited opposition, winning his final term in 2005.
Nothing's stopping Congress from insisting that the coup cancels aid to Egypt. But nothing's starting them, either. In the last six months, conservatives were actively talking about cutting aid to the Muslim Brotherhood-dominated government as it kept fulminating about backing out of the Camp David Accords. (Governments do things like that to make people ignore the collapsing economy.) There's rather less worry about the military government.
UPDATE: Pat Leahy, chairman of the Senate Judiciary Committee, insists that "U.S. aid is cut off when a democratically elected government is deposed by military coup or decree." That's what the law says, certainly, but you know laws—they're such vibrant, living documents!
UPDATE II: And here's the president.
[W]e are deeply concerned by the decision of the Egyptian Armed Forces to remove President Morsy and suspend the Egyptian constitution. I now call on the Egyptian military to move quickly and responsibly to return full authority back to a democratically elected civilian government as soon as possible through an inclusive and transparent process, and to avoid any arbitrary arrests of President Morsy and his supporters. Given today's developments, I have also directed the relevant departments and agencies to review the implications under U.S. law for our assistance to the Government of Egypt.
Review, not cancel. No mention of the C-word.