Militarily? They won't even have to.

Your empire has rotted from the inside out and is on life support. You will fall like the Soviet Union and all of its subjugated states with it. The difference is that vastness and resource richness of that region, the hardiness of its people and the collectivization of everything gave them the possibility to recover. People in general didn't have to die from hunger or severe deprivation. It wasn't a pretty sight for the longest time and yes they've suffered severe insult upon injury, but they survived and recovered nonetheless.

The West, with all of the fucking migrant hordes it had to tolerate because its leadership had been either hijacked, adhered to lunatic neoliberal ideologies or had foreign interests, will collapse, starve and completely vanish.

Again, energy is the Achilles heel of the West. Then it outsourced farming. Then it outsourced production of virtually everything, steel and chemicals being some of the most crucial ones.
The whole world has been emancipating while 'mercuh and the NATO block became drunk on their own "full-spectrum dominance unipolar theory" and fucking sold out everything that was to be sold in favour of a horseshit "service" economy.

It's finished. Done. The moment you saw huge cities succumb to "multiculturalism" i.e. being invaded by subhuman hordes from all corners of the world was the time you should've known it was already too late. It's been going on at least since Bush and Clinton and it only picked up pace, snowballing into an unstoppable disaster.