We could take on Iran with Russia, China, Pakistan, Afghanistan, and all the other Stan’s being the supply lines some what similar to Vietnam with six additional countries added, with the Iranians who appear to have the willingness to fight to the end.
How does it work long-term for the USA? In time the United States would have to build up to half a million men on the ground. The United States at its peak in Vietnam for example had over half a million men on the ground.
The biggest reason the Ukrainians are holding their own first and foremost is they are willing to fight, second is the supply lines. Vietnam won because they were willing to fight and they had China and Russia as their supply lines.
Afghanistan against the Russians, and Afghanistan against America was the same. The Afghans were willing to fight as long as they had material coming in from the USA and the same was true when they were getting all their supplies from the Chinese, Pakistan, when they were fighting us.
Supplies are important, but what’s more important is whether or not a group of people have the heart to fight to the end no matter what.
I would, like you, draw comparisons with Vietnam.
I think this means that the US is going to get stuck there for a very, very long time, as there are downsides to all options including pulling out, which may in turn survive a change of president.
On the other hand, all it takes is a president who doesn't care about the downsides, or thinks the downsides are worth the cost, and suddenly Iran's free to toll the strait, and a whole bunch of other straits get tolled in turn. If Iran gets away with it, I wouldn't be surprised if Israel finds Gibraltar closed to their shipping, though Suez would likely remain open to them for the foreseeable future.
I very much hope that Trump doesn't take the literally nuclear option here. A different Pandora's box to letting Iran take their toll, and a much worse one for everyone.