America is more than ready, considering how much we spend on the military. This article is a few years old, and definitely sensationalist, but is still an interesting read-

https://www.wearethemighty.com/mighty-trending/how-long-the-us-military-would-last-against-the-rest-of-the-world/

And on top of that, the US Army just started deploying robotic troop carriers, and is finishing up remote combat vehicles for the front lines so that first contact isn't with soldiers. Yes, we're going to have killer robots on the front line. And soon.