Yeah, attacking a military unit seems like an act of war to me. Pretty blatant. Demonstrates that China only behaves as a bad actor with its neighbors, and can't be trusted to be anything other than a bully.

This is basically China daring the US to do something about it. We shouldn't take the dare, but we should respond with a show of support for the Philippines. China is flexing because they think the US is too busy with Ukraine, Israel, and the upcoming election.

Well, according to China, those waters are their territory, which means that the presence of foreign military vessels is an invasion.

Practically speaking, I think you could call that area a contested region, so minor skirmishes like this are expected and could escalate to war (like Crimea eventually did).

I think that the Philippines approach has been something like, 'You can claim those waters if you want, but you can't possibly keep us from entering them, so we're just going to ignore you until you start killing our people, and then we're gonna call in big brother America.'