That 51 were just killed in a Ukrainian cafe is so commonplace there that it is not a big news story here. According to the Office of the UN High Commissioner for Human Rights (OHCHR), there have been 26,015 civilian casualties in Ukraine. This includes: 9,369 deaths, 16,646 injured, 500 children.
If there was some sort of natural disaster that killed and injured hundreds of people elsewhere in the world, the US would be sending aid and medical supplies. We'd be assisting in digging through rubble, piling sandbags, fighting the forest fire or whatever was needed. We help countries to recover from and avert natural calamities. Not many Americas question the humanitarian aid when they know a particular country was subjected to Mother Nature's wrath. Few would ask if the country was "worth it".