Why? They only ask us for material support, not troops, to defend against Russia, a known international pariah, attacking to conquer their country. Early on, we committed more to the effort, but the trend presently is more support coming from the European Union, with overall US $128 billion (.55% GDP) and European Union $124 Billion, the largest Non US contributors by GDP being Germany (1.31% GDP,
UK (.93% GDP) and Canada (.67% GDP). Ukraine has supplied all the bodies and boots on the ground in their defense. If we give Ukraine to Russia, which country will they want next? If we had not disarmed Ukraine, with assurances, Russia would never have attacked, but not Trump want to walk away.