Sure, but the American government's entire point is to collect American taxes and provide benefits for Americans. To minimize monetary cost and maximize benefit to American lives is exactly what it should be doing.
It’s only impossible because people like you refuse to see it’s possibility. If enough people see it’s possibility. It becomes not only possible, but inevitable.
You would have to overcome the combined political and military might of every country in the world to enact that system. How about you work on getting basic healthcare to people first. That actually might happen in your lifetime.
Because every effort devoted to unobtainable utopias is effort detracted from being politically effective in the current system and erodes the legitimacy of the left wing. And besides, most communists are hoping for revolution, and not actually helping people.
That's not revolutionary at all though is it. That's just what normal people do. My local conservative Christians are revolutionary by that definition.
The best reason there is, to have something to dream for. We see it in tons of our literature, look at how popular Star Trek is. It's not the crazy sci-fi stories that had people coming back, it was the world the audience wanted to live in. I wouldn't stomp on someone's dream like that. Especially when it is widely impossible, like who cares? It's their dream.
It's shortsighted to think that global communism is achievable within a human lifespan just as it is to assume that system won't be as vulnerable to corruption as current systems are. However that's beside the point, why advocate for something so widely impossible; because maybe it gives people hope that things may get better. If it was possible I'd definitely take more interest cause I don't think it'll work out how a lot of people who advocate for global communism think it will, but it's not possible.
Because politics actually matter, and for every person LARPIng about trying to make star trek a reality, is one less person working towards achievable goals making an actual difference in our actual systems. If all of the commies stopped preparing for the revolution and started voting and being proactive in their local party politics, they'd probably be surprised how much they could get done.