Of course the AWL 'stands with workers in the underdeveloped world' against imperialism - in the struggle for equality, social justice, trade union rights, and so on - and, of course, beyond that in the struggle for socialist - that is, international - revolution. What we do *not* stand with is the self-aggrandising posturing of local bourgeoisies - like military adventures to impose their will on small groups of people who don't speak the same language, etc - or nationalist mythologies they tell their workers to obscure the truth of the international system.
'Argentina' - as some classless entity - is not 'oppressed by imperialism.' Fighting for 'independence' for Argentina is pure mystification. Workers' rights, not to mention socialism, require a struggle against the international social and economic system, not 'independence'. 'Indpendence' can only mean, in practice, some sort of disconnection from the world economy (Argentina's had enough of that!). And *no* kind of independence is meaningfully expressed by the military seizure of islands in the middle of the sea where no Argentines even live.
The term 'semi-colony' (about which there has been enormous, critical Marxist literature since at least the late 1970s) is a confusing one in this context. There are meaningful contexts - for one example, Egypt from the 1930s to the fall of the monarchy, when it was a formally independent country with a huge - direct - amount of control from Britain.
But to define a country as a semi-colony by virtue only of the relative weakness of its bourgeois state and capital to other, bigger, states and capitals, is to collapse Marxist categories into populist ones. Your operational theory is 'dependency theory', developed by bourgeois economists to explain Latin American subordination to US capital, and then adopted by a certain type of radical anti-imperialist in the 1960s.