I am not saying what should or shouldn’t occur. In short, the unity only goes as far as the interests permit. National interests of any rational player will always supersede any intentional perceived or otherwise unity, regardless whether we agree with those interests or not.
In this case, the United States attempts to save some of the reputation, while likely not entirely productive because it is viewed for what it is and otherwise inconsistent actions on their part. They cannot stop facilitating the course of actions chosen by Israel (this refers to the unity discussed here), but they also cannot “muscle” Israel into what they think those actions should be (as has been observed over the past couple of months). So they implement this policy change/reversal due to the pressure from the international community, including the allies (which again refers to the unity). Hence, the best (likely the least) they can do under the circumstances, acting in their own interest (that we may or may not agree with).
Consider another example. United States said in very straight terms that they would go to war with China over Taiwan. The French, German, and other Euros said in terms that were just as unambiguous that they would not if that were to actually happen.
What about the French, Lithuanian, and Estonian officials suggesting that it may be a good idea to send troops to Ukraine, whatever that means, while most other allies said it would never happen?
What about Hungary and most of the rest of the EU? Turkey and Hungary in NATO? Poles talking about temporary closing the Ukrainian border? And then there comes internal politics, such as the security aid bill in the US, etc.
There is only unity as long as the perceived national interests of every party align (provided some party(ies) cannot exert (undue) influence on others). More realistically, there are likely various degrees of unity on certain issues, including security. Of course, the main assumption here is that every party acts rationally, which is often further limited by the irrational constituents of the said parties.