This is a fun trope that's parroted but none of these wars were the same or even really close to each other in goals.
Vietnam - actually has great relations with the US and we won the peace.
Iraq - well they had Saddam and now they have a functioning parliament and things seem to be going a lot better for them. Was it worth $1.5 trillion of US spend to achieve that? That's a better question.
Afghanistan - We wanted to provide schooling for little girls and stuff like that and, well, the population didn't want it. So at some point you cut your losses.
Iran - We're not going to like invade and occupy Iran, though we could. We're just going to have to keep blowing up their military capabilities until they have a more reasonable government.
> As for "end up in another war", the language you chose is very revealing. You don't just "end up in...war". Wars don't start themselves. Someone starts them and in the case of the US, it's almost always the US.
It was just a figure of speech - Ukraine wound up in a war.
The US usually starts the war because the US is the only country in the world actually trying to do anything about nefarious actors. Easy to criticize from the sidelines, which is why American foreign policy has shifted to - we don't care what militarily irrelevant countries think about our activities because, well, we don't and they don't matter and we don't really care what they think. It sounds bad, but if we just retreat to isolationism as the MAGA and far-left crowds want, well maybe Iran goes and builds 5x the missile capabilities we have now, then they close the straight, force the gulf states to capitulate, and now you've got a nuclear armed Iranian regime in control of 20% of the world's oil supply. Oh and now you have nobody there to save you because China isn't going to go sail boats over there and bomb Iran, and Europe certainly isn't. Now what do you do?
Ironically, I used to teach English in Vietnam and my wife is Vietnamese.
The US didn't win anything. What Americans call the "Vietnam War" was and is called the American War in Vietnam. The country was absolutely decimated and left with scars that are still healing today (see for instance Agent Orange). After the US fled the country, it continued to wage what amounted to an economic war against Vietnam, excluding it from the global economy. Into the 90s, Vietnam was one of the poorest countries in the world. My wife's parents had relatives who survived the war only to starve to death after the war.
Vietnam, largely because of its geography, is a very smart and pragmatic country. It's the only country in the world that has comprehensive strategic relationships with the US, China and Russia.
> The US usually starts the war because the US is the only country in the world actually trying to do anything about nefarious actors.
The good old, "I had to beat my wife because she wasn't acting right!"
> Iraq - well they had Saddam and now they have a functioning parliament and things seem to be going a lot better for them.
An estimated 300,000 to 1 million Iraqis died as a result of the war. But yeah, they have a parliament and "things seem to be going a lot better for them."
> Afghanistan - We wanted to provide schooling for little girls and stuff like that and, well, the population didn't want it. So at some point you cut your losses.
Do you actually believe anything you write? The US went into Afghanistan to get bin Laden and attempt to eliminate Afghanistan's role as a safe haven for Al Qaeda. Ironically, through Operation Cyclone, the US directly supported militant Islamic groups during the Soviet war, and where do you think the Taliban came from?
> Iran - We're not going to like invade and occupy Iran, though we could. We're just going to have to keep blowing up their military capabilities until they have a more reasonable government.
Iran has about 4 times the land area and double the population of Iraq. Given the amount of debt the US has and Trump's ecstatic destruction of Pax Americana by defecating on all of America's most important alliances, I think the most optimistic scenario is that the cost of making the Persian Empire again would destroying the American Empire.
They won the peace (and the war). You didn't win shit. You lost, badly. The wound in the American psyche by this defeat will never heal, to the point we have to witness claims such as yours.
> Afghanistan - We wanted to provide schooling for little girls and stuff like that and, well, the population didn't want it. So at some point you cut your losses.
So you lost. Mainly because you went on a military adventure, with unclear goals, with a population you didn't understand. Much like in Vietnam!
And here you are, in Iran.
I think the one lesson you did learn is to heavily control the media and the narrative. Body bags and mission failures are bad press. Lesson learned.