American army commanders consider crossing the border with Ukraine: the 101st Airborne Division

Could the US troops enter the territory of Ukraine and what would it change? The commanders of the 101st Airborne Division said 'they are ready to fight at any moment' and that 'in case of escalation, they are ready to cross the border with Ukraine.' What is the official position of the American administration and how to perceive hints made by both the military and the ex-director of the CIA?