I understand the impulse to not want to support other countries who don't seem grateful for the aid -- but this sounds like one of those "cutting of your nose to spite your face" situations. Even if you're annoyed that a recipient of US aid is insufficiently grateful, and even if you think NATO allies should be paying their 2% ... a key question is still, "Do we prefer the world where the current-aid-recipient is unsupported?"

If the US prefers the world where Ukraine is not annexed into Russia, then even if our support is not appreciated to your satisfaction, it may still be best _for the US_ to provide the support.