We don’t have the military wherewithal to back up a war guarantee to the Ukraine. From Douglas MacGregor at theamericanconservative.com:
The Biden administration appears willing to get us into a fight we’re not ready for.
Conflict with Russia may be inevitable. Kiev’s strident threats to resolve the crisis in Eastern Ukraine with force of arms, combined with Washington’s refusal to acknowledge that Moscow actually has legitimate national security interests in Eastern Ukraine, makes it so. Equally troubling, the president sees no particular reason why he should explain to the American people why Washington’s readiness to support Kiev’s use of force against Russia makes strategic sense for America.
In 1937, when the Imperial Japanese government expressed sincere regret for attacking and sinking the U.S.S. Panay, an American gunboat that had been patrolling China’s Yangtze River, U.S. Ambassador to Japan Joseph Grew was not satisfied. He warned the Japanese Foreign Ministry that “Facts mean more than Statements.”
In 1937, President Franklin D. Roosevelt decided not to retaliate against the Japanese. FDR knew there was no public support in the United States for a war with Japan or any other great power. FDR also resisted pressure from the U.S. Navy’s admirals to retaliate because he knew America’s armed forces were not ready for a full-scale war. As for our British friends, they were not ready to weaken their fleet in the Atlantic to join a fight against Japan when the threat of war with Germany was growing.