I don't understand why most people think that the Jedi would only be wiling to have a flat out battle. They do not like fighting, and if they can win in any other way, they would do that first. Meaning, whether they're in the same place or scattered throughout the world, they would first find the points of infiltration and infiltrate. They would use politics, mind tricks, and stealth to do what they need to do.
The US would not be able to handle them, especially if it's 300 freaking Masters. The Jedi aren't going to move into a position or be in a position where the US can use heavy weapons, and will have to send soldiers. Jedi Masters in urban settings would annihilate soldiers, since they can sense where they are, can sense ill will, and influence the mind (not just mind tricks, but coercions that are a lot more subtle), and even if the fight happens, the Force will have them move faster than the soldiers could track them, and take their enemies out with the Force.
Jedi are not mindless warriors with lightsabers just swinging it around. That is supposed to be their last possible resort. It doesn't matter if they can deflect bullets. They sense the soldiers preparing to fire before the soldiers can, and they can take them out with the Force from a good distance away, stop the bullets with the Force, or move so they're not even there when the soldiers actually do shoot. It doesn't matter if they can stop artillery, because the Jedi will always be on the move and be in influential positions in the US, meaning it's not going to be places the US can afford to bomb.
Both Knights and Masters would have a hard time if the US knew they were the enemy, so round 2 would be difficult though not strictly impossible for Masters. Just because the US knows that they are the enemy doesn't mean the US knows all of their faces. And if they were all human, then they could easily infiltrate the US.
Round 1, I don't think the US has much of a chance. There is way too much of a range of difference in ability between Knights to be sure, and though that exists for Masters as well, the weakest Master is still more than powerful and crafty enough to win.