Would it be good if, as part of a lesson, we were given Latin sentences that some words/grammar/syntax were purposefully placed wrong that we would have to try figure out?
Not when you're using "in" I think. Not sure why you can't use the locative and drop the "in" though. It is consistent throughout the course for America, perhaps because it's not a Latin word?
As Quidam Cragius said, the locative case in an exception, and very rarely used, it's only for cities, towns (big or small), and small islands. Not for countries, continent, etc...
Yes, and the locative is not used, we use "in" + ablative for the other cases.