Act of cowardice?? China can only push Philippines and other small nations around, tell us about courage when you get control over taiwan, you 50cents have been crying for decades, try pushing USA out of the straits and not small nations south of you and then think you have the "courage".
Your...
How does the Air force make sure the planes or equipments they buy are not bugged? A virus could lie dormant for decades and then activated at the right time...
Question shouldn't be what did US expect?
Question should in fact be what were the Chinese thinking trying to set up an ADIZ and asking all military planes to comply with when they don't have the power to enforce it? No surprise that US will show them who is the boss.