The change in attitude began with Trump. He was to first president to bring the threat of China to the mainstream political discourse. Since then, China is so objectively a threat to the U.S. economically, militarily and through their direct actions of manipulating U.S. businesses, countering our influence internationally, that bipartisian support was easy to flourish once someone actually took an anti-china stance.
The power of the Chinese market, low wage labor, sophisticated and concentrated foreign policy manipulation, and their stated strategy of "hiding their strength and biding their time" (until Xi), has worked to make the U.S. turn a blind eye. The problem of China has been present to any competent political scientist for a while now. But the amount of money incentives and ignorance on the part of U.S. business and political leaders made it so they would in essence be bribed to ignore the issue.
Obama did a pivot to asia, with the TTP at its helm, but in reality after 8 years of presidency and negotatitions, the results were nothing unfortunately. TTP is debatable as a solution. Even with the TTP, the U.S. has been losing 300 billion a year to China in trade. Granted this results in cheaper products for us, but 300 billion dollar trade surplus for China is what funded the communist dictatorship growing military spending, leading to a military that can be as powerful as the U.S.'s one day. 300 billion each year is more profit that what all the U.S's top tech companies make each year combined. The rise of China is not a miricale, like Japan's, Koreas, and other early east asian miricales, it was bought by America's consumers and political inaction.
Some theory, although depressing admittely: There is no government for governments, so each country lives in anarchy. Therefore nothing is off limits to get what you need to survive, including war. Countries go to war and act in self interest because, if they are not strong, whoever is will likely use their power to exploit the other country.
A balance of power brings stability. If there is 1 superpower, the world becomes globalized ( US after fall of soviet union). No world wars, because anyone who fights the dominant superpower will lose. This is called unipolar, one of the most stable and peaceful states for major powers.
Now when another power comes to rise, it is like a startup rising to crush the industry monopoly. Except, instead of having to battle it out economically, they can litteraly kill each other (or on the scale of countries, war).
The incentives for major war skyrocket
Britian was was the major power, they controlled 3/4ths of the world through their colonies and their unstoppable navy. Then industrial revolution and trains led to the rise of land powers, and the rise of Germany's economy. The rising powers, the disruption the balance of power eventually led to the world wars.
After that was U.S vs Soviet Union. The two sole superpowers after WW2 were on the brink of the nuclear war. for about 50 years.
The soviet union collapsed because communism with corruption was unable to keep up with captialism.
Now the U.S once the sole superpower, faces the rise of China. The chances of World War 3 are higher than ever, although they have calmed down from the high tensions of year or 2 ago.
I am sorry to be the bearer of bad news, but I think it is important that we finally realize the immense threat that China is. Not just economically, but for our safety. Their goal is to be the top superpower, and to make the U.S. and anyone else bend to their will, as is every countries goal