[yfzhou]

Because the US military is not about defending trade, arguably it's the very opposite: it is China's goal to protect global trade as it is the biggest trading partner of most countries, while the US invests heavily to maintain the ability to disrupt trade of any country it thinks is benefiting too much. (e.g. the first island chain for blocking China's access to the seas - https://en.wikipedia.org/wiki/First_island_chain)