Regarding the nationalism fork:
(From memory) Mahatma Gandhi wrote at some point that if all India achieved out of the freedom struggle was independence from the British it would not make the struggle worth it at all. As I have lamented before, it has been high fashion the last decade or so to play down his thoughts and actions, but if we look beyond fashion we would see that he was quite correct (in the thought, and the wide range of reforms and processes he based upon that thought/framework). So, it seems to me, there is no necessity at all for leftists (at least humanists) to base their theories and actions on *axioms* of nationalism/sovereignty etc. British imperialism was a bad thing in the same way that exploitation by the rich ("capitalists" (*)) is and the leftist reasons to oppose them on this [common] basis are necessary and sufficient. "Anti-imperialism" is best used as shorthand.
IMHO,
--ravi
(*) As always, I use quotes not to scare those of you who seem to fear them, but only to indicate that my usage of the quoted term indicates common/accepted/received usage and does not imply that I fully understand its definition. IOW, I have only a very murky idea of what "capitalist" means (as employed in meaningful sentences).