98% of the time when you see a military aircraft, it's because all the military does when not actively fighting a war is practicing to. We would literally just go up and fly circles around the airfield, practicing a few normal approaches with a touch and go landing, then a few practice aborts, then some combat approaches, then some instrument inly landings. Day, night, good weather, bad weather. Practice flying high, low, pressurized, unpressurized. There's 500 ways to land each airframe, and every pilot in every unit needs to practice each type dozens of times a year or more to keep their pilot qualifications. And it's not just the pilots. The hospitals **practice wartime medicine, and the maintenance guys practice their craft in Chem gear. The LEOs pretend there's an active threat on the base and a thousand other types of exercises. It's a big part of what our military budget each year goes to, and it's why, while we have a LOT of issues in our military that need fixing, we don't have the types of problems you see Russia having with entire units defecting or surrendering, losing aircraft/equipment so frequently, and it's why so many of us come back alive. The US hasn't seen personnel losses like Russia has seen in Ukraine since WW2. The price of that is a lot of money and a lot of time spent practicing, even at home.
Most likely, if the US were going to be attacked, you wouldn't find out because jets were flying overhead, you'd get an emergency broadcast on your phone telling you to stay in your house or move to a specific shelter site or provide some other type of instructions or you wouldn't see it coming at all because nobody else did either.