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Re: your question about the different engines in the US Fit versus the European market Jazz - I don't know for sure, but I suspect that Honda US went with a slightly larger engine because they were concerned about the odds of being able to sell a car with a 1.2l engine (the one that you cite which gets ~50 mpg). The acceleration probably just isn't enough for US consumers.
More likely, though, is that they didn't want to risk the cost of federalizing the engine without some sense of whether or not the car would sell.