Trotskyism isn't a real ideology. They have no actual beliefs. If you ask them what "socialism in one country" even means, either they will just straw man it and claim that Stalin believed you can have socialism in one country as a permanent and unchanging state of affairs, or they will just reduce it to pure pedantic arguments over definitions.
In the first case, it's obviously false, as Stalin argues the direct opposite in Foundations of Leninism that capitalism is a global system and thus socialism in one country is going to be inevitably dragged into international politics, and that socialism needs global victory to guarantee against capitalist restoration in the long-term. Many Trots will say this almost verbatim and pretend they are disagreeing with Stalin even though you can just read FoL and see that is Stalin's position.
Socialism in one country was not an argument that we should only build socialism in one country, but an argument that we can build socialism in one country. It was a response to the Marxists who argued that the Bolsheviks should abandon socialist construction after it was clear the international revolution had failed and they would be isolated for some time. Stalin argued that they can build socialism in one country as a temporary state of affairs to later help facilitate revolutions in other countries.
Other Trots just transform it into a purely definitional disagreement with no material substance. They will say that, by definition, socialism is international, so socialism in one country is by definition impossible. If your country has overthrown the bourgeoisie, expropriated the means of production for the working class, and replaced production for exchange with production for use, it is still not socialism by definition because they say the definition should include "+ also it's international."
This is just definition mongering and doesn't have any practical implications.
Trots fit into two categories.
Some really are just MLs in denial with Stalin Derangement Syndrome. Nothing in ML theory says you have to worship Stalin. You can, if you wish, be an ML who just is critical of Stalin. But these kinds of Trots just make it their whole personality obsessing over Stalin, constantly bringing him up in every discussion, and try to pretend there is some big ideological definition between Stalin and Leninism which doesn't exist.
They can't just say "I don't like Stalin" and move on, they are obsessed with making it their whole personality and ideology, and making sure everyone knows who much they hate Stalin, calling everything they dislike "Stalinist" and trying to pin all problems on Stalin personally. Just search the word "Stalinist" in any Trot article and you will see it said multiple times. They are so petty that Trot parties will often refer to themselves as "Marxist+Leninist" rather than "Marxist-Leninist" because they argue that Stalin used "Marxist-Leninist" first and gave it cooties and so they cannot use the dash and so they replace it with a + or the word "and".
Others are leftcoms in denial, although some don't even deny it. They will call themselves Trots but then copy/paste leftcom rhetoric which Trotsky himself argued against. I have seen so-called Trots for example claim that you shouldn't have a revolution at all in a poor country like Russia was, which is a leftcom take but something Trotsky strongly denounced as that was the Menshevik position.
Again, Trotskyism has no real ideology, so a person telling you they are a Trotskyist doesn't tell you their beliefs. They always have some other underlying belief, which is either Leninism or left-communism, and what unites them is just Stalin Derangement Syndrome. They also are united in opposing all real-world attempts to build socialism, arguing they are all influenced by Stalin and therefore are all "Stalinist" and should be condemned.
So-called Maoists, who don't even read Mao, are basically just utopian socialists. They don't believe in historical materialism, which argues that the economic base is derivative of the material conditions and is thus ultimately not something you can "decide" but forms itself unconsciously. Human societies do not have the "free will" to decide their economic base. It is determined by the historical conditions at that time.
What you can "decide" is only the superstructure around it: the political system, property rights, etc. Utopian socialists instead believe that you can indeed "decide" the economic base and try to force the economic base to be a particular way according to their moral philosophy, but this leads to economic devastation, hence the Gang of Four saying "it is better to live under poverty" than to stop trying to enforce a particular morality onto the economic base which was destroying the economy.
Their utopian socialist vision of the world is just not economically viable, and so every Maoist revolution inevitably will just evolve towards "dengist" reforms when they actually are faced with building a real economy in the real world that has to take into account their actual material conditions and not just morality, so Maoists will support a revolution until it actually succeeds, then they will condemn it. Maoists also end up opposing every actually-existing socialist project, viewing themselves as holier-than-thou because those projects have abandoned the Maoist morality and so the Maoists see themselves as morally superior to it.
