The USA, USSR and UK in their primes could all be characterized by their massive populations, continent(s) of natural resources, large industrial production, scientific advancement and relatively stable government. Assuming a PoD even as early as 1800 gives limited options for who can compete: India, a China-or-Japan-led East Asia, a Mexico-or-Brazil-led Latin America, Germany or a French Empire. There might be a few other candidates, but the rest are unlikely to have the scale necessary to become a true superpower on that time scale.
A great power on the other hand only has to match another great power's combination of population, natural resources, industrial production, scientific advancement and stable government through some combination of their own. This allows some trade-offs: WW1 Russia had a much larger population than Germany and many more natural resources, but Germany had more industry and generally more innovation which more than balanced our the weaknesses. Generally though there is a "minimum bar" for each of the five aspects that a country needs to be a great power.
In terms of taking steps to increase a country's power:
We now know pretty much all of the natural resources that would be extractable in the past. If your country needs natural resources either have them find a now-known deposit earlier, have them conquer something or plausibly invent a reason why they have more advanced extraction techniques to take advantage of resources they couldn't OTL. Failing those options, the country can also buy the goods they need abroad. They'll need a way to supply themselves in a war or national crisis but this method can be viable with the right allies.
Industrial production can be difficult to establish but the basics are pretty well established. Look at what Japan did in the early 20th century and what the Asian Tigers did post WW2. Generally you want a country to start with simpler goods like clothing, move on to early industrial goods like steel and then move on to advanced goods like cars, airplanes etc.
Stable government can be instituted fairly quickly if done perfectly, but is also very hard to do right. Even if the government is chaotic over the long term, like in Italy or France for the last 150-200 years, a sufficiently united country can keep things organized enough that the country can still function in the long run.
Scientific advancement requires the correct investment. This takes time - a generation or more. Make sure your country isn't winning all the Nobel Prizes a decade after the first university is founded.
Population is the hardest to change. Broadly speaking New World countries, like the USA, Mexico, Brazil and Australia can increase their population through immigration, while Old World countries are reliant on birth rates. This means that for Old World countries what you have in the historical record OTL probably isn't that far off from what you'll have ATL. New populations from annexation or colonized subjects can slowly be integrated over time but this can take hundreds of years. New World countries can increase their population much faster, but they're also much lower to begin with. Whether New World or Old World it probably takes 100 years or more to get a country up to the "minimum bar" necessary for great power if it wasn't there OTL.
From your above list, some of those countries are fairly easy to elevate to great power while others are virtually impossible.
Chile with a PoD in 1900 simply doesn't have enough time to increase its population up to the level necessary for great power. In 1900 the Chilean population was 3 million, and in 2018 the population is 17 million. Both of these are well under what I'd consider the "minimum bar" for great power in those years. I suspect that Chile, being mostly mountain, coastline and desert simply can't sustain a large enough population to compete with the great powers in any modern era.
Brazil is much easier. If you want Brazil to be a great power in the second half of the 20th century, you can use a 1900 PoD. Even if you don't touch the population you'll have a population of 50 million by 1950, which is probably above the "minimum bar" of that period (minimum bar is a rough estimate in any period). The natural resources are likewise more than sufficient for a great power. Instead you can focus on increasing Brazil's industry, education and government stability, which is certainly improvable with 50 years of improved decision making over OTL.