I am a Marxist in China
Orthodox Marxists in the Chinese internet community often view Russia and Iran as weak links in imperialism, rather than as anti-imperialist forces .However, in the view of Chinese Marxists, opposing the global hegemony of the United States takes precedence over opposing secondary imperialisms (Iran, Russia).
The person in the picture is Yang Heping, a US citizen with a Chinese green card, and he is the most popular orthodox Marxist-Leninist-Maoist self-media figure on the Chinese internet (with 3 million followers on Tiktok and 800,000 on Bilibili). Yang Heping advocates that whether it's Ukraine, Russia, or Iran, "the truth is on the side of the proletariat, not on the side of any government or capitalist."
In China, those who unconditionally support Iran and Russia are usually nationalists or national leftists.
I wonder if the differences between the left-wing in Europe and America and the left-wing in China are really that significant?
You miss understand imperialism. Imperialism is not simply whenever a war is not about national liberation. Imperialism according to Lenin is about the need to export capital. Russia exports mostly goods and resources. The world Bank lists Russia as developing nation. Foreign direct investment outflows out of Russia are negative. Russia is not imperialist. The capitalist class in Russia would make better profits without the war, even if they had lost the Ukrainian sphere of influence. The reason Russian capitalists need this war it to defend assets inside Russia from NATO imperialists. In repeated negotiations to prevent the war, NATO did not accept yes as an answer from Russia to their demands.
On the other hand, US capital would not survive without the forever wars. US absolutely needed this war, that's why they started it. Remember, Putin wanted Russia to join NATO and become subservient under US. US didn't accept, because of the absolute imperative to have war.
But granted, Russia was probably on the edge to become imperialist. It's not as straightforward as in Iran's case, where I think the case could be made much more easily to speak of a war of national liberation.
As I understand it, Lenin’s definition of imperialism was not based on a capital surplus, but rather on the proportion of monopoly capital or finance capital within a country. If one looks at the balance of capital inflows, Tsarist Russia—long a net importer of capital from Britain and France—certainly would not qualify as an imperialist power; yet, aside from Lenin, you would be hard-pressed to find anyone else in the world who was more intent on destroying Tsarist Russia.