Can’t speak for other countries, but in China we had very bad experiences with the Trotskyists (Chen Duxiu faction). The Stalinist/Comintern faction (Wang Ming) was also problematic, and Mao gave Stalin a 70/30 assessment, but with the Trotskyists, he completely trashed it. (There is a reason why Mao is so revered in China, for he succeeded in synthesizing the correct path for Chinese socialism, which could have easily ended in disaster had it gone down either of the other two paths)

The Chinese Trotskyists condemned any sort of collaboration with the KMT nationalists when Japan was literally invading at the doorsteps. For them, it is better for China to be colonized by Japan if that meant it could arouse workers solidarity across all the countries that are being colonized by the imperialists.

Trotskyists believe that international workers solidarity is the most important part of socialism, and strictly condemn any sort of collaboration with right wing nationalists, even when the country is under threat of fascist invasion. Mao wrote scathing remarks regarding such views in his essay on the role of communists in national wars, arguing that nationalism (in the third world sense, not in the European national chauvinist sense) is an integral part of internationalism and you cannot have internationalism without nationalism.

Note: to be fair to Chen Duxiu, he did eventually come to correctly identify the nationalist struggle as the principal contradiction for China at the time, and did renounce Trotskyism, but his tainted reputation would not be restored until the 1990s.