Firstly, welcome to the forum.
You raise an interesting question but one that is rather hard to address. I'll confine myself to the US, since I'm not knowledgeable about the Australian case.
The desire to cultivate "infant industry" can be traced back to colonial days, during which the salutary neglect of British enforcement of the Navigation Acts led to the start of native shipping industry--those that later bore the brunt of the taxation. Hence, to complete gut the USA of the idea that led to the protection of industry will be quite difficult.
It might be easier to have it suffer political defeat. Tariffs were vary controversial in early American history since Southern planters (who bought refined goods) had to pay them while Northern industrialists benefited from them. A POD might be that the early Tariff policies are defeated--perhaps Alexander Hamilton is sick or dies even earlier. Perhaps the Democratic-Republicans are more successful against the measures in the 1830s. The downside however is that all of the angst that historically went to criticize big business will still exist, and it will now have the pleasure of deriding foreign interests as well. Certainly the first time America tries to fight a war and finds itself reliant on other nations for bare necessities of warfare will engender concern. Also, I'm not sure what the economic results of the tariffs might be. Without tariff protection, British manufacturers will have an easier time competing in the US, but transportation costs will come to impose a natural tariff at some point, so US industry will still develop.
However, will there still be capital to fund it? OTL British capital underlay a surprising amount of American economic activity in the 19th century: most of the cowboy ranches of the American West were ultimately financed and sometimes even owned by British bankers and financiers. Such returns still exist to be sure, but if British companies are even more competitive in the US, then surely some of the capital that OTL funded American industry might fund other ventures. Might a consequence of the political concern about big business and foreign competition and the need to supply war efforts lead to greater state-funded, state-run manufactures? Perhaps.
At bottom, the problem is that much of the policies of the 19th century find their inspiration in the 18th and hence a mercantile frame of mind. Furthermore, I would have to say that the economic advantages of free trade are hard to defend from the bottom of the totem pole: witness the widespread aversion that still exists today, despite the experience of the Great Depression (and its links to protectionism, among other things).
Thanks for your reply nichmacheus. Some interesting issues you raise will give you my thoughts on most of them.
In Australia, like the USA, the tariff was a controversial political issue when first introduced in fact it was
the political issue in the period 1900-1910. Predominately industrial areas in south-eastern Australia, in particular Victoria were highly protectionist in leaning, whereas agricultural areas such as Queensland, Western Australia and to a lesser extent New South Wales were more free trade (although prior to Federation only the New South Wales government was avowedly free-trade). This distinction continues to this day with the move towards free trade since the 1970's being most controversial in Victoria and most welcomed in Queensland and Western Australia.
Basically the reason is for similar reasons as in the USA, tariffs raised the cost of manafactured good, which therefore raised the cost of agricultural production. However as agriculture was export-driven they had to accept world prices. In Australia, this led to a system of agricultural subsidies and price supports to farmers and I assume similar in the USA. Without a system of protectionist tariffs I presume that these subsidies may never have existed? Or could a significantly revised form of economic interventionism instead of being aimed at supporting struggling industries ( tariffs for manafacturing) be aimed at further enhancing export-led sectors (subsidies for agriculture? Note that Australia even after the conversion among all governments to free trade in the 1970's and 1980's, maintains statutory single-desk marketing for some agricultural exports (Australian Wheat Board, etc).
Back to the USA, the increased economic dominance of the agricultural sector would presumably dramatically alter the political balance in the USA. How would this alter the general animosity between the North and South leading to the American Civil War? Of course moral repulsion towards slavery and the desire of the North to stop the secession of the South led to the Civil War, but (at least accoring to my university history lecturer) one of the main causes of the growing anti-slavery sentiment in the decades prior was the shift in economic power from agricultural slave-owing areas (South) to industrial abolitionist areas (North). In other words, as their economic power waned, the South faced an increasingly difficult task to push their political agenda.
Taken as given, that the USA without protectionism would still have a predominately agricultural base how would this effect the political balance of power? My theory is that with the economic base still in the South, it would be impossible for abolitionists to turn the obvious moral case against slavery into an effective political case. I assume that there would be no Civil War and that slavery would last a decade or two longer. Probably no longer than that, as the international pressure to abolish slavery would become unbearable. Possibly threats by primarily the British to boycott American products in favour of non-slave nations (Australia, Canada, etc) would lead to abolition. It would be interesting to see the implications of this, perhaps less historical animosity between North and South and more suspicion especially in the South of other nations.
In regards to the question of British finance of American business I agree with your point. One of the main reasons for British investment in American manafacturing was of course to get past high American tariffs. With this gone I can't see British financiers investing in most American sectors, except for agriculture. Unless, of course the US were with domestic capital to develop some highly efficient niche manafacturing industries, which the British might then find profitable to further in invest in. Same for all above points with Australia, in fact due to its much smaller population base Australia would find it extremely hard to find the domestic capital to invest in its industries until much later that the USA.
I agree that after its initial early stage of development, that at least some form of industry would develop in both the USA and Australia, as transportation costs would be un unofficial tariff. So you would basically see all sectors of the economy still going as they were in reality it's just their share of the economy that would substantially alter. I think the notion that either proctectionism or free trade would
absolutelylay waste to and eliminate certain industries is something of a myth. Of course this all changed in the 1960s(?), with the containerisation of freight eliminating a lot of the transportation cost.
The point you make about the effects of a war are quite valid and would certainly have influenced protectionist pressures. The 'What will we do if trade's blocked off or other nations refuse to trade with us in a war' argument is one of the most commonly used arguments against free trade and specialisation in trade (in fact I have heard similar fears used against Australia's current reliance on China for cheap manafactured goods!). The counter-argument is of course that no nation in history has had trade boycotts by
every other nation in the world (if America in the 19th century went to war against one European nation, then there would certainly be other European nations eager to trade in its place and supply the US with materials). The biggest threat would be if the US found itself in a war against Britain (after 1812), due to the Royal Navy's maritime supremacy, there would be the realistic threat of an effective naval blockade. Perhaps the US would early on find the need to build up a very strong US Navy, much earlier than in reality, in order to counter this possibility as well as to protect trade routes in the Atlantic and Pacific. Not much of the above applies to Australia, owing to our reliance (rightly or wrongly) at the time on British 'Imperial Benevolence' to protect us against external threats.
I do certainly see the quite sensible and realistically unavoidable need for both nations to build up a self-reliant military industry, so your idea that most manafacturing could be state-owned or at least state-subsidised and furthermore geared towards military production. This would exist between wars but would get periodic boosts at the outbreak of war. Perhaps this sort of 'War Socialism' would give a ideological boost to more interventionist governments in peactime, especially in the USA, where of course there is a strong historical feeling against this.
Finally, I do agree that free trade is rather a hard thing to argue from the bottom of the totem pole, seeing as all current free-trade nations (including USA, Australia, etc) have been protectionist at some stage. As a free-trade supporter myself, I know from talking to other people how deeply held some people's almost instinctive belief in protectionism is. It is seemingly easier to argue the merits of self-sufficiency and even autarky than it is to explain the merits of compartive advantage and specialisation. Perhaps a turning point could have been an aggressive trade war by the UK against the USA in the mid-19th century, which made the USA feel that it's natural self-interest was better served by specialising in certain products for the British and other markets?