I never said that Britain was justified in any way in the Opium Wars, far from it. But that's irrelevant to my point anyways.

Britain had ulterior problems than the trade imbalance with China. Throwing out 2.6 million pounds of opium (weight) and refusing to talk about it as you denied an embassy, because you saw yourself as a higher form of civilization than those pesky barbarians in the east of the world did absolutely nothing to help, which is why incidentally Russia France and the US were supportive despite not having the same problem as Britain. Refusing to consider a peace treaty, torturing POWs, killing messengers and so on is also a good part of why the opium wars actually went through, there were quite a few times parliament almost shut it down, and I'm pretty sure were it not for the insult that Qing China kept imposing due to their frankly stupid feudal bureacracy and It is true that opium had a large part in it and the British did like the tax revenue it gave. But, as it happens, the fact that China wasn't particularly interested in British manufactured goods isn't relevant to that question, because the fact that China wasn't interested in industrializing its vast worker base has nothing to do with the benefits of industrialization.

Your analysis of steamships is incorrect, by the way. 6 British steamships sunk hundreds of Chinese ships, and were able to manoeuvre in ways that Chinese didn't know were possible at all. They also single handedly destroyed hundreds of artillery pieces and by virtue of being able to access shallower waters and going against wind and current so easily they were able to attack Naval fortifications from a side they weren't designed to protect from, destroying them, and were able to carry firepower comparable to entire Chinese fleets. Read about the individual Naval battles in the first Opium war, it's actually incredible just how efficient steamships were since the very beginning of the Opium Wars. They were literally a hard counter to the entire Chinese arsenal, except for land-based artillery of course.

My claim of GDP being a good proxy for military capability was prefaced by specifying it applied to industrialized warfare only. And it works pretty damn well, actually, if you take into account morale and readiness. Not realizing it at the time is a mistake that Hitler made invading the USSR, costing him his life, and a mistake Hirohito made despite the warnings of Yamamoto, which lead to Japan losing WW2. Its pretty damn accurate assuming two stable nation states and factoring in the monetary equivalent of throwing bodies at the enemy.

Yes, the Naval blockade of the US couldn't use steamships because they didn't have enough of them to block the entire shoreline of the US while keeping them supplied. The geography of the Chinese blockades were incredibly different. Chinese logistics were centered around the main rivers, since, you know, no real infrastructure. The British only had to blockade rivers in order to cripple the Chinese economy.

China being a huge exporter of low-value added goods and materials, it was simply impossible for Britain to balance the trade equation. The fact that that simple proposition had to lead to a war is a good insight on why we got rid of the gold standard.

Also, even before the industrial revolution, I can think of about 10 counter examples to production capability being the main driving force behind military victory, actually. Logistics and keeping your armies fed was possibly the biggest factor behind pre-industrial empires.

Saying that the industrial revolution brought no benefit to warfare until the later half of the 18th century is positively ridiculous. Using industrial weaponry European powers were able to impose disgusting imperialist régimes in a flash, because it was a huge advantage. To most of their enemies, it simply was economically and technologically (two sides of the same coin) impossible to fight back. But you can figure this one out yourself :)