I'm assuming you're on platforms dominated by Americans and Westerners so you're not seeing it much, but I can assure large portions of the world are quite happy to see America's downfall in real-time.
Personally, I hope to see China fill the void America will leave behind; the world will be better for it.
I think a more likely outcome is nobody filling the hole America leaves behind, and the incentives of a multipolar world are much more brutal then that of a unipolar world, as a result I expect a rise of new nuclear armed states.
No not at all. The vast majority of Americans are uninterested in being world policemen when it means it's mainly American boys (and girls, but mostly boys, let's be real) dying in foreign wars.
The Chinese are not stupid enough to send their kids to die in war, and even if they were, they at least have an excess of young males.
Personally, I hope to see China fill the void America will leave behind; the world will be better for it.