Fast enough.
We'll have plenty of warning before the Chinese land. Don't know who else could. I'm not sure I wouldn't trust myself to the tender mercies of the Chinese before I'd trust all of MY neighbors with unlimited small arms.
Unless they have us beat before the invasion. That's a possibility, not in today's world but a world. Have no idea how that would work, except that they could absorb more punishment and keep coming than could the US the way things are now.
Don't know anyone else on the horizon for that scenario.
Arf