"The United States is very concerned by the People's Republic of China's provocative military activity near Taiwan, which is destabilising, risks miscalculations, and undermines regional peace and stability," State Department spokesperson Ned Price said in a statement.
"We urge Beijing to cease its military, diplomatic, and economic pressure and coercion against Taiwan."
The United States has an abiding interest in peace and stability across the Taiwan Strait, and will continue to assist Taiwan in maintaining a "sufficient self-defence capability," Price added.
"The US commitment to Taiwan is rock solid and contributes to the maintenance of peace and stability across the Taiwan Strait and within the region."
Taiwan's Foreign Ministry thanked the United States for its concern, and said China was increasing tension in the Indo-Pacific region.
"In the face of China's challenges, our country's government has always committed itself to improving our self-defence capabilities and resolutely safeguarding Taiwan's democracy, freedom, peace and prosperity," it said.
China has yet to comment on its activities, and it is not clear what may have caused Beijing to decide to mount the missions, though Friday was the country's National Day, a patriotic holiday that marks the founding of the People's Republic.
It has previously said such flights were to protect the country's sovereignty and aimed against "collusion" between Taiwan and the United States, the island's most important international backer.
Taiwan's defence ministry said it sent combat aircraft to warn away the Chinese aircraft, while missile systems were deployed to monitor them.
It said the aircraft were a mixture of J-16 and Su-30 fighters as well as anti-submarine and early warning aircraft. Friday's flights included nuclear-capable H-6 bombers.
Taiwan Premier Su Tseng-chang condemned China for its actions on Saturday, saying the country was engaging in military aggression and damaging regional peace.
Taiwan marks its national day next Sunday, with a major speech by President Tsai Ing-wen and military parade in central Taipei, which will include a fly-by of fighter jets.
China has stepped up military and political pressure to try to force Taiwan to accept Chinese sovereignty.
Taiwan says it is an independent country and will defend its freedom and democracy.