I believe that it has become almost impossible for the Arab countries to unite in the face of any common enemy
This is not an accurate statement.
When you say Arab countries, there is the Arab regimes and the Arab people.
The problem is that most of these regimes are dictatorships installed and/or backed by USA. These authoritarian regimes depend on US so they will obey any orders that comes from Washington and Washington supports the Zionists because US is controlled by them.
But then there is people who don't follow their dictators. For example we have been seeing this in Jordan. The dictator Abdullah (or as Arabs call him کلب إسرائیل) supports the Zionists but not Jordanian people. We see the mass protests in these countries. We have even seen military personnel from Egypt and I think Jordan too enter occupied Palestine and eliminate dozens of Zionist terrorists before being martyred themselves.
What you are also forgetting is what some refer to as the United States of Resistance. Majority of the Resistance are Arabs and they are well united with an unbreakable bond.
Take their latest operations in the past week, Yemen from 1500+ km away, Iraq from 500-600 km away and Lebanon from 50 km away are cooperating in hitting Targets in occupied Haifa and Mediterranean sea. I believe Yemen is launching hypersonic missiles while Iraq overwhelms radars using drones and Lebanon provides reconnaissance in a beautifully synchronized operation. And they are all Arabs, and what I said is just a small part of it.
It is unfortunate that at the beginning of the nineties, Saddam moved his forces towards Kuwait to occupy it (instead of directing them to Israel). The Arab countries agreed to an alliance to confront the Iraqi aggression against Kuwait at the same time that they did not unite to move their forces against Israel when it occupied the Egyptian Sinai and the Syrian Golan and Lebanese Shebaa Farms.
Exactly what I said above. The dictators obey US regime's orders. Before Saddam moved on Kuwait, he moved on Iran. US orders were to support that invasion but then US orders were against the other invasion (Kuwait) this is why the dictators acted completely differently, they supported and supplied the first but opposed the second.