It does insofar as the US can "decide" to betray all of its allies by ignoring its obligations under a military alliance. We've already publicly proclaimed to

It does insofar as the US can "decide" to betray all of its allies by ignoring its obligations under a military alliance. We've already publicly proclaimed to the entire world that the American military will come to the aid of any NATO member which is invaded. We've never had such an agreement with the Ukraine and thus owe no obligations towards them.