I think everyone is really overreacting to the idea of F-16s being given to the Ukraine. First of all, the deal hasn't been completed yet, and it wouldn't surprise me if it never is. There is a reason Poland and the US were so sketchy when it came to sending MiG-29s last year. There is only so many times you can poke the bear before it takes a swipe at you. Up till now Russia has actually show remarkable restraint when NATO sent mercs, AA systems, artillery, but sooner or later even Russia is bound to reach it's limit and will escalate.
Second, just how much use will these F-16s be. This is a weapon system. It needs a place to take off and land. It needs to be supplied with parts, engines, fuel, bombs, missiles. How about a competent ground crew who know what they're doing? Perhaps you can take a Su-27 pilot and train him at Nellis for a month or two to operate the plane, but what about the ground component for maintaining an unfamiliar weapons system? When a couple of screws come loose or a pipe comes off somewhere deep in the plane making the machine unable to fly, will it just be written off? Will they push the plane couple hundred kms to check it in Poland?
Third, is the question of what F-16s will be sent. They won't be the newest planes (block 50/52 and up). They'll be F-16 MLUs, planes which already have been ridden hard for decades. The youngest of those planes will be what? 30-35 years old? And if NATO decides to send anything more advanced, it will be depriving itself of usefull assets. Will Poland send theirs and basically deprive itself of a combat air force? Will Greece weaken itself vis-a-vis Turkey, when Turkey is inching closer and closer to leaving NATO? Or will the Americans stretch themselves even thinner?
What's curious to me is that the Americans seem to be OK with F-16s being sent do the Ukraine, while at the same time being so opposed to sending long range weapons which might be used to strike against Russian soil. Who wants to bet how many F-16s will get shot down while trying to bomb the Kremlin? I can already see the western media OOOh-ing and AAAh-ing when Zelensky proudly anounces that the first-ever F-16 has flown over Russian airspace (completely ignoring the fact that it cost the pilot's life).
Given how many resources these F-16s would require (on top of 4 types of tanks to be sent and God knows how many artillery systems already being sent) I wouldn't be surprised if the next logical step for Russia was to start concentrating their missile attacks on railway lines coming through western Ukraine.