America's history is basically one long story of internal divisions, briefly overcome primarily during economic booms. The last economic boom, the computing/internet boom, was particularly long lived and helped create the longest window of internal stability we've had. That boom's coming to an end, and the era of stability it brought probably isn't that far behind. And this is before you even stop to consider things like social media which helps amp up and accelerate divisions by orders of magnitude.

If the root cause is external, it’s easier to stomach. But what if this is just America, attacking itself? That’s a lot harder.

There's also the whole South China sea thing, where they're making claims on international waters and the territorial waters of their neighbors: https://en.wikipedia.org/wiki/Territorial_disputes_in_the_So...

But I have a feeling your position is basically "Except for all the cases where they're threatening their neighbors, they're not threatening their neighbors at all."

Arunachal Pradesh.

https://www.nbcnews.com/news/amp/rcna245797

Tibet and Xinjiang already conquered and we have forgotten about them.

Pretty much anything that happens to abut the South China Sea.

I suppose you could also make the argument that they already did invade Tibet and Hong Kong, though that's splitting hairs.

India, Bhutan. South China Sea. East China Sea/Japan.