all I've seen is an invasion by the US that has further destabilized the region, and fueled a huge rise in extremist sects.
The situation in Iraq is surely deplorable. It is probably going through the worst period in its modern history. But this doesn't mean it can't be undone.
Fundamentalists are present everywhere in the world and they just need the right conditions to cause havoc (like a war), but they surely are not the majority. Such a scourge is caused more by misery and ignorance in the poorest strata where people get successfully manipulated by a bunch of opportunists, than by some kind of zealous adherence to a religious ideology.
Most people in the Middle East want change and they are definitely against fundamentalism. They are seeking better lives and are getting tired of their governments and of the whole mess. Even the most reactionary regimes will eventually bend under pressure.
I don't think that a united middle east is even possible until the US stops its meddling, which is just one of many reasons why we need a technate in North America first to put an end to all that
The rise of new powers like China and a possible resurrection of Russia might aid in shifting the US regime's focus away from the Middle East. Other than that, I agree the only other possible solution is the end of the current regime in the USA.
Then the work can be done on uniting the place (good luck)
A lot of religious and secular movements, whether pan-Arabic or pan-Islamic, have been trying to achieve this. Such movements have existed for more than a century (some of these ideas date back to the first Islamic conquests, like the "Islamic Umma") and have been very popular at different times before being persecuted by colonial invaders and by the regimes that replaced them. But without external intervention, with proper handling of parasites and with mutual respect between different nationalities and religious and ethnical minorities, nothing can prevent the Middle East from doing a better job than the EU.
if there's any oil, water, and arable land left
Yes, that might be a problem, but not only for the Middle East. With the abuse of natural resources, with radical climate changes in the near future and a rise in temperature by several degrees in the next decades, the Mediterranean and African regions could be the first affected, but it would inevitably turn into a worldwide catastrophe. Just imagine those regions becoming totally uninhabitable and hundreds of millions of people being forced to flee to the "north". Imagine the reaction of the "northern" countries and all the possible scenarios (eg: genocide). One more reason to put an end to the current regime before it's too late.
and even then most likely only to join a larger technate, such as Asia, Europe, or Africa.
Yes, a technate on such a scale would definitely be a logical outcome.