The idea that the US border is not being defended is a huge lie. Another lie is that its possible to defend the US border. The US border is huge and US unlike Ukraine is not being invaded. Immigrants coming over the border are harder to track then groups of tanks. We spend and arguably waste billions on billions of dollars on border security in america with nothing or negative results. That's not because of some nefarious pro immigrant agenda its because practically the border isn't securable.

As for Ukraine, discouraging Russian aggression is in the intrest of America