I am forever frustrated by how the United States seems to be the be-all end-all in warfare from the first world war onwards. Barring exceptional circumstance (i.e. global alliance), they simply cannot lose. At what point is this condition set in stone? At what point in history is it certain that a single power will dominate the North American continent and thus be unchallengeable by outsiders, and how can that be prevented or altered?
The American Civil War was the last chance. An alliance of the CSA, Britain, France, and the Mexican Empire could--if they had chosen--battered the US down and partitioned chunks off. Ideally, an earlier POD involving foreign intervention in the Mexican War would do something similar. But afterwards, the United States will grow its economy and become dominant that way (and if/when needed, put a lot into the military), or if pressed, militarise and become dominant in that way (albeit economically weaker).
I am operating under the assumption that no matter what power takes control of North America from one ocean to the other will be indomitable. Is this accurate? If not for the idea of American Exceptionalism and Manifest Destiny, would the west have been developed in a timely manner?
In short, what would it take for an Asian, African, European, or even South American nation to be able to project power and hold global influence in the same manner as the United States does currently?
An early enough POD is needed for any of those countries. Asia has China, Japan, and Korea (the latter needs Manchuria, while Japan needs Hokkaido and Sakhalin much earlier than OTL), all of which could have serious power and have a role like the US. Asia also has Russia, since Siberia has a lot of nice land and especially resources to power the Russian economy and war machine. Africa also needs early PODs (before the dominance of Europe became assured), but South Africa up to the Zambezi in the hands of a power like Portugal could be like an ideal version of Brazil which could be a great power and one undefeatable to foreign foes due to its remoteness. Europe only has Russia--anyone else is checked via great power alliances, and Britain being much stronger than OTL seems ASB (unless it keeps the 13 Colonies I guess). South America (and Latin America as a whole) needs a better colonial period (I don't believe surviving Inca or any other native empire would amount to much but a local version of Siam) to make better land transportation networks. Even then, I think Argentina is the best chance there. Basically have Spain settle the coast of Southern Brazil and not lose it to the Portuguese, and have an independent state consisting of modern Argentina, Uruguay, Paraguay, most of Chile and Bolivia, and the Brazilian states of Rio Grande do Sul, Santa Catarina, and Parana (and maybe parts of Mato Grosso do Sul and Sao Paulo). You have similar factors to the US--rich agricultural land for plantations, rich mountains full of minerals, a vast amount of agricultural land which can belong to anyone who stakes a claim on it, a country of several different regional cultures coming together for one purpose, etc. You even have some coal and oil (in Chile and Patagonia respectively) for industrialisation. It wouldn't be as strong as the US, but it would still be stronger than any European great power barring maybe the Russians/USSR.
Potential Game-changers
1. France retains Missouri/Louisiana
2. Missouri becomes an independent nation
3. USA loses the Mexican War
4. Confederacy is formed peacefully or wins independence early
There may be others that would work
1.5. Britain substantially defeats USA in 1812-1815
1. The US without the Trans-Mississippi area still has the bulk of the population and resources which built the US. It still has a lot of oil in Pennsylvania, Ohio, and the Gulf. It still has the pull factors to lure a lot of immigration. And now it has a key rival in the form of whatever state emerges in Louisiana, leading to a stronger and more active US militarily. So this US is still easily a great power which can decide wars.
2. What do you mean? If Louisiana is divided, then the US has even less to worry about in that area and can pit the two against each other to check that potential threat.
3. The US still has the Plains, much of the mountain states (borders can be adjusted with Mexico in other wars/purchases), and will certainly seek a route to the Pacific. This US is easily great power tier, and stronger than any other great power, with agricultural output to influence the world, Texas/Plains oil (in addition to other US oil, the main loss being California oil), the minerals of the Northern Rockies, etc.
4. Depends on their borders, but if they lack Missouri and Kentucky and New Mexico/Arizona, the US doesn't have too great of a loss. And once again, this gives the US a significant foe to build up an army against and gain crucial experience in that field which the US struggled with going into World War I.
5. The US which results from this will certainly struggle against the British in the future, and will ally with France (and perhaps later Germany and/or Russia) to achieve its goals. And there will come a time the British can't win in North America if they want to win in Europe.
OTL the US had a strong navy and weak army until the mid-20th century. Here we'll see a stronger army and the navy will also/instead include a substantial riverine fleet to fight Louisiana, the CSA, or British Canada.
Nuclear warfare poses its own challenges, and serves to mitigate the effects of geography substantially. Therefore, it is only marginally pertinent to the discussion.
Having allies across the globe certainly has a great effect. However, it cannot be enough on its own. If the USSR had allies scattered around the way the US does, it would still be hamstrung by the Bosphorus, the Danish Straits, and the Sea of Japan. Additionally, the United States has not the worry of overland invasion, and so can devote more resources abroad. A competitor in Europe would have to be exceptionally powerful in order to maintain dominance over its neighbors and still compete with the United States. And finally, the two-ocean aspect of the United States is also a substantial advantage.
However, my question was not on the theory of challenging the United States, but rather the particulars. Thanks to Grey Wolf and Seafort for their contributions, but even there, those seem to be ways to simply lower the level of power for all countries, not bring another up to the level enjoyed by the US. So how could this last one be accomplished? At what point in history could another true challenger arise, able to match the United States in global power projection and influence, and possessed of similar industrial capacity and economic power? Some speculate that China may fill this role soon, but for now let us discuss only the past.
A Russian Empire that rolls all sixes, as in it is able to live out it's full industrial potential, would be comparable to the U.S. Apparently, even in the mid 19th century , some famous author pointed out how it seems that Russia and America are likely to control the destinies of their respective hemispheres. An alternate China could also dill this role, but it would be harder and more complicated than just simply empowering Russia.
China certainly, especially controlling the borders of the Qing Empire at their maximum extant and with Korea as a close ally and even having forced Japan to bow to them (as occurred at several points in history). Russia as well--if the potato is widespread earlier (and not the "devil's apple") and if we add quinoa to the Columbian exchange (as it could have been), then we have two solid cold-weather crops which can make European Russia powerful, and at that point we only need to open Siberia and encourage settlement there.
The Russian Empire was a feared great power, and the USSR took on that mantle, and the biggest reason the United States has any advantage is that the geography of the US is more conducive toward developing a navy.