But for some scholars of the region, the concrete benefits of all that engagement pale in comparison to the size of the American efforts.

“When you look at the cost-benefit analysis, there is a limited payoff, and the United States is going to reduce its footprint over time because there are so many other things to deal with in the world,” said Gary Sick, a Middle East scholar at Columbia University who served on the National Security Council under three presidents.

A similar view of the region has shaped the approach of both the Obama and Trump administrations. Despite the drastic differences in their words and style, both have viewed the Middle East primarily as a source of nuisance that siphoned resources from other American priorities. Both presidents called on regional powers to play a greater role in protecting and governing the region.

The immediate desire to step back was driven by battle fatigue after years of deadly combat in Iraq, and a feeling that American military investment often did not make matters better. But scholars say that longer term shifts have made the region less central to America’s priorities.

American protection is no longer necessary to ensure the free flow of oil from the Persian Gulf, for example, and a boom in domestic production has made the United States less dependent on Middle Eastern oil anyway. Israel now boasts the region’s most effective military and a strong economy while many of its neighbors are in shambles, making it less dependent on American protection.

“The reality is that our direct interests in terms of protecting the American homeland are very few in the Middle East,” said Mr. Sick, adding that the record on American interventions doing more good than harm was at best mixed.