If China tries to take Taiwan by force, it would spark WW3. There are US military bases in Taiwan [0] which would automatically ensure that the US military is involved in any such attempt.
[0]: https://en.wikipedia.org/wiki/United_States_Taiwan_Defense_C...
US-China relations were OK under the Obama administration. Note that the Trade war and the cultural divide were initiated mostly by the current administration, and on balance, have done little to improve US standing or economy at the cost of straining Sino-US relations. They appear to have been mostly targeted at improving domestic standing by the administration. As such, it is reasonable to assume that a different administration can lead to better relations.
As to the bigger question of how the US can deal with another Superpower: that is a much harder question to answer. What's clear is that China will be a far more powerful rival than the Soviet Union, whose economy was mostly subpar and never really matched that of the US. It seems that Obama admin wanted to expand the US sphere of influence with the TPP; basically supercharge the economies in the immediate vicinity of the PRC with the help of the US to "contain" it. But the PRC has been a step ahead, and has cultivated allies using the same strategy that the US adopted: huge amounts of aid. Especially in Africa.
There are other factors that will make it even harder to predict the best approach in the future: Climate Catastrophe is already upon us, and its going to get a lot, lot worse in the future. Just look at how the PRC was able to handle the pandemic: if the US is unable (or unwilling) to take decisive actions to contain pandemics and natural disasters, it will cause permanent damage to America's economic capacity. This pandemic alone has cost the US over 370,000 lives, while the PRC (reportedly) has lost less than 5000. Despite this abject failure, the ruling party actually won more seats in the House (although they did lose the Presidency and the Senate, but only barely). This does not bode well at all for America's capacity to handle the severe challenges that it will face in the next few decades.