The Malacca straits will certainly be important, but the US will have to reach past China and Chinese allies to the south to blockade it, and will be sitting ducks for drone and missile attacks (see the black sea fleet for a demonstration). China has heavily invested in submarines to avoid exactly this situation.
Authoritarianism in China has a significantly different flavor to US authoritarianism. The US is serving the goals of their dominant elite industries - finance and tech. China has an engineering culture amongst the elite, and is inclined to solve problems with productivity and megaprojects rather than handing money to purely extractive industries.
For an example of the difference between their flavors of authoritarianism and the outcomes they bring, compare their health care systems - the USA has one of the most expensive in the world at ~$14,500 per capita, and poor outcomes due to privatized corruption, while China's 14th 5-year plan has brought universal health care for approx ~$650 per person. China's average life expectancy is higher than the US's.
The US is, objectively, extremely corrupt, and is transitioning to authoritarianism to protect that corruption. China's authoritarianism achieves measurable goals, and has broad (though not universal) public support.
The USA will get curb stomped in a war. They just don't have anything but a massive military buildup from decades of pork barrelling unnecessary military contracts. Their population is sick and stupid. They have alienated their allies. They will lose.
