Either Polish retards raring for a fight, or just Ukr interceptors missing and flying over the border. Russia if they wanted can directly attack Polish infrastructure.
If its the former, I guess it actually makes Russia smart to have pulled back east of the Dnieper.
America itself wouldn't want to join. They would end up in a stalemate that fucks all future prospects of NATO. I wouldn't rule out Poland seeking some fascist glory, but actually isn't too likely either because Poland just purchased a lot of weapons which haven't arrived. Bad timing. Not to mention Poland can do a much more clear cut false flag.
So almost certainly interceptors missing.