I am sorry, but thats absurd. There’s much to dislike about US foreign policy, but to believe that the US has territorial ambitions on Chinese mainland belies a deep lack of understanding of US foreign policy.
The US wants to remain the only regional hegemon in the world. To do that, in needs to maintain a degree of military and economic supremacy over China and with its network of allies have credible potential to contain China in case of conflict. Not in their wildest dreams would they ever want to annex Chinese land: that’s far, far more trouble than it’s worth. The US annexed the Philippines, but there was far too much opposition against incorporating them as a state which eventually lead to granting Philippines their independence. That annexation took place in an age when such things were still commonplace and acceptable. The opprobrium alone of annexing China’s eastern coast is reason enough why the US would never even contemplate it.
The best scenario for the US would be to have China as a vassal state, who they can exploit for economic purposes, like the colonial powers did in the 19th century.
America would not conduct de jure annexation, but set up a de facto annexed puppet state after invading Taiwan, in the same manner Russia established the Donetsk and Luhansk "republics" to control Ukrainian land.
That is territorial ambition, and their actions and words show it. They are massing weapons, troops, political support, international "recognition" for an offensive. You are the absurd one to not recognize this naked aggression.
It may not be realistic than US offensive would succeed, but it is their dream, no matter how unrealistic. On June 23 2023, Biden declared he will move 400+ million $ worth of weapons to separatists fighting the government in China. The Taiwan Travel Act signed into US law 2018 lays the groundwork for American officials to encourage an attack on China.
There's just 20 million living on Taiwan. 200 000 US troops can occupy the region, and the surrounding islands which are barely inhabitated. It is not entirely unrealistic threat, if the PLA wasn't there to hold them off.