Invalid reasons for getting more deeply involved in the Syrian civil war continue to be heard. One of the latest is in a front-page article in the Washington Post, which declares that America “increasingly is being viewed with suspicion and resentment for its failure to offer little more than verbal encouragement to the revolutionaries.”

The neoconservatives who run the Washington Post continue to beat the drum for more U.S. war in the Middle East, now giving voice to influential Neo-con pundits demanding that the Obama administration begin lethal aid to Syrian rebels, as ex-CIA analyst Paul R. Pillar notes.

Andrew Tabler of the Washington Institute for Near East Policy is cited in the article as arguing that unless the United States furnishes significant lethal aid to rebels, a virulently anti-American variety of Islamism could arise among disillusioned Syrians. If the United States maintains its current policy, “ultimately the political entity that comes to power is not going to be in U.S. interests,” says Tabler. “A secular and democratic Syria is what we’re going to lose big-time.”

The Post’s correspondent is no doubt reporting accurately some of the sentiments she is hearing from impatient rebels. And in a general sense, U.S. policies toward conflict-prone portions of the Middle East do significantly shape popular sentiments, and those sentiments do have significant implications for U.S. interests. But this is not just a matter of buying gratitude with lethal support.

The recent experiences of the United States with its most extensive efforts to intervene in (or to touch off) civil wars are instructive. The amount of U.S. aid and effort in them should have bought mountains of gratitude. One is the very long-running civil war in Afghanistan.

Although it is not true, as some legend has it, that the United States created Al Queda with its aid to the jihad against the Soviets, and although the Afghan Taliban was Pakistan’s child and not America’s, U.S. support and involvement in Afghanistan do underlie much of what bedevils that country and the United States today.

U.S. lethal support gave an important boost to Gulbuddin Hekmatyar, and it was even more important in developing into an effective fighting force the Haqqani group — which is now so much of an antagonist to the United States that it is the subject of Congressional resolutions urging the Secretary of State to designate it formally as a foreign terrorist organization. Some gratitude.

Then there was the war in Iraq, sold partly on the idea that the United States would be lovingly showered with gratitude from Iraqis welcoming Americans as liberators. The war did not, of course, turn out anything like that.

Even when events in Iraq have enjoyed an uptick or two, Iraqis have been slow to credit the United States for anything that has gone well and persistent in blaming the United States for much of what is still not going well.

Several things are happening to account for these results and can be expected to happen again if the United States were to immerse itself more deeply in the current conflict in Syria. One is that there never is much genuine gratitude in the first place.

There is at most a tactical “enemy of my enemy is my friend” approach by belligerents willing to take aid from the devil if it will help them to win the next street battle. When circumstances change (as they will when Bashar Assad falls), the illusion of friendship is dispelled.

Even as long as a common enemy remains and circumstances are largely unchanged, the provision of assistance creates the expectation of still more assistance. Failure to fulfill growing expectations leads to growing resentment. Attitudes tend to be shaped by asking “what have you done for me lately?”

Aiding any one set of contestants in such a conflict opens one up to resentment and anger from other contestants — even when they ostensibly are allies of the aid recipients but even more so when alignments change as a civil war and associated political struggles move into new phases. It is good advice to try not to play favorites, but that would be exceedingly difficult to do in the complicated Syrian situation.

The most important dynamic is that if the United States gets involved at all in a bloody mess, it tends to be seen as responsible for all of the bloodshed and mess, even beyond what is reasonably attributable to its actions.

Even if the United States does not apply the Pottery Barn rule to itself, others do, and in an expansive and unfair way. This will be a major hazard with Syria, given the prospect of much bloodshed and mess there still to come.

The perceived power of the United States amplifies and sustains such sentiments, much more than the actual power of the United States enables it to shape and control circumstances for which it will be blamed. The United States will not lose a “secular and democratic Syria” no matter what it does, because such a thing is not America’s to lose in the first place.