Our problems are the left keeping the gloves on our military. If things went so far south in the wot, with russia/iran/syria/china keeping on running interference, I would hope for a President that would let our guys cut loose. We can't be beat. As my (soldier) nephew said, "we could literally take on the world".
I wouldn’t be so arrogant to say “we can’t be beat”
Or military (hands down) is magnitudes more lethal than those countries you listed. But under the right circumstances our noses could be bloodied conventially. We are the best, but we are not unbeatable.
And remember, Russia holds the ultimate trump card (granted, we’ve got it too) - nukes, a lot of them, and the means to deliver them