Do you think your computer chips (Apple M1, AMD Zen, etc. etc.) are going to be readily supplied from Taiwan under these conditions? Is this annexation good and proper for the world? Is it a benefit of US interests to let this happen?
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China has no ability to attack the USA domestically. The issue is what China can do in the Asian-sphere of influence, and whether or not that's net-benefit to us in general.
Not just China either, North Korea almost certainly would flatten South Korea and take over it without the US military presence holding the DMZ. We've also been able to force a peace between Korea and Japan by outlawing Japan's military, and promising protection of Japan with our forces. A lot of our foreign influence and politics revolve around military strength, both the good and the bad.
EDIT: Finally, pirate attacks are virtually nonexistent. Any pirate dumb-enough to try to take over a ship on the high-seas is obliterated by the US Navy. For better or for worse, we actually need a strong navy (with special ops units) to hunt down would-be pirates and discourage them from popping up.