The United States, per the Budapest Memorandum of 1994, is contractually bound to defend Ukraine.
That Memorandum was signed three years after the collapse of the former Soviet Union and at the time, Ukraine had the third largest nuclear arsenal in the WORLD behind the United States and Russia. To coerce Ukraine into transferring its arsenal to its former fellow Soviet state Russia (for further arms reductions), President Bill Clinton, Russian President Boris Yeltsin, and Great Britain's Prime Minister John Major assured Ukraine of its sovereignty and defense in exchange for eliminating its nuclear capabilities. No one alive at the time would have imagined that within 30 years, Russia, under its Dictator Vladimir Putin, would break the treaty--twice--by invading Ukraine and that the U.S., led (in name) by a sick Putin sycophant named Donald Trump, would take sides with Russia by falsely blaming Ukraine for the latest war, and by demanding that Ukraine beg and bow for U.S. assistance that, per that old Budapest Memorandum, it "should" be providing anyway!
Trust, if Ukraine was still sitting on the world's third largest nuclear arsenal, Russia NEVER would have invaded and Trump wouldn't be trying to pimp the nation's vast mineral resources. But just like the U.S. has broken treaty after treaty with Indigenous American tribes over the past 200 plus years, I believe that Ukraine MUST turn to the European Union to supply all of its armament needs! Indeed, as a longtime student of world history, I also believe that several old U.S. allies like Taiwan, South Korea, Germany and Japan had better be prepared for anything because the U.S., at least while under MAGA control, is NOT to be trusted to uphold treaties that provide for mutual defense and stability.