“I’ve been admitted to Carnegie Mellon (School of Computer Science), University of Michigan (CS in College of Engineering), UCSD (Undeclared), Northeastern (CS and Business), and UBC (Canadian uni, also for CS)”
Wow.
For me this would come down to Carnegie Mellon, Michigan, or maybe UBC. Any of these would be superb. Northeastern is also very good and their coop programs would be a great thing to participate in as a CS major. If you are Canadian then UBC is a bargain, other than the housing costs, and with the weak Canadian dollar it might be relatively affordable in any case.
I would be a bit concerned about going from undeclared to CS at UCSD. If you can get into CS then it is also very good. I suppose that if you can stand sunshine then the weather is not so bad there.
You are in at multiple great universities. I would just forget about UCLA and UCB.