"Why US condemns occupation in Ukraine and yet supports occupants in Gaza?"

It's because of how this clusterfuck started after WW2 and the Holocaust. A group of nations (including the US) thought the Jews should have this contested land after all their troubles. This may have been a bad idea, but it's impossible to change now. Now Palestine and Israel are at war, because both of them wouldn't let the other nation live in peace and they are unable to agree on anything. The US is still allied with Israel. Palestine should have requested international help with foreign soldiers protecting them. They took matters into their own hands against a much stronger opponent. Now it's too late. They will likely be eradicated in the next few years. It will be like they never existed.