Why does China react to US war consignment to Taiwan?

Beijing [China], September 8 : After the United States announced USD 1.1 billion worth of military equipment to Taiwan, China came out with a vociferous response.
The sale of military equipment to Taiwan includes Harpoon and Sidewinder missiles, according to the Defence Security Cooperation Agency (DSCA).
The US State Department approved an estimated USD 355 million in sales of Harpoon Block II Missiles and related equipment to Taiwan in a bid to modernize the island's defence capabilities and serve US security interests.
The State Department also approved the sale of Block II Sidewinder Missiles and related equipment at an estimated cost of USD 85.6 million. The possible sale of USD 665.4 million in Surveillance Radar Program support and equipment was also approved.
Insisting that the latest arms sales and are for defensive purposes, the Biden administration said this will not alter the basic military balance in the region.
This comes amid already heightened tension between Washington and Beijing over House Speaker Nancy Pelosi's Taiwan trip. Pelosi's trip to Taiwan this month triggered a new round of tensions in the region.
Following the visit of the US delegation, Beijing launched large-scale military exercises in the vicinity of the island. China's ruling Chinese Communist Party views Taiwan as part of its territory and vows to "reunify" the island with the Chinese mainland.
Over the latest arms sale, China on Wednesday said "China has always been unequivocally against the US's military contact with Taiwan and arms sales to Taiwan. Taiwan is a province of China. There is no such thing as defence for Taiwan".
"US arms sales to China's Taiwan region violate the US's political commitment in the three China-US joint communiques, especially the August 17 Communique. By selling arms to Taiwan, the US is supporting and conniving at "Taiwan independence" and creating new factors that could lead to tensions in the Taiwan Strait," Chinese Foreign Ministry spokesperson Mao Ning said during a press briefing on September 7.
"The US side needs to strictly abide by the one-China principle and the provisions of the three China-US joint communiques and stop using Taiwan against China. China will act resolutely in response to acts that undermine China's sovereignty and security and interfere in China's internal affairs."
Writing for Geopolitica.info, Valerio Fabbri said China responded to US military supplies to Taiwan with aviation intrusions into Taiwan's ADIZ.
"Beijing decried the military deliveries as undermining Chinese sovereignty and a violation of the three joint communiques signed by the United States and China, which it interprets as a guarantee by the United States to reduce arms supplies to Taiwan," he said.
Fabbri said it seems China is trying to display strength, but it is failing miserably at the same.