Here are the short answer to your discussion questions:

No I was not aware of St Frances Xavier Cabrini at all - but then I am British and atheist, so I'd have to be well out of my lane to have come across that information.

The issue with Columbus is specific though, even within his own timeframe he was considered a cruel renegade - and there's plenty of evidence he transgressed the bounds of acceptability even in his own epoch. It's possible to retrospectively turn him into a hero - but such an undertaking is likely worth more effort than it's worth. Colorado are right to distance themselves from it - but they're also right not to jump immediately to tokenistically fill the gap.

I don't think it creates complexity or confusion for a state to celebrate a holiday that's not a federal holiday. I think Colorado has likely got this one right - but I think the entire idea of celebrating a single person is inherently problematic as someone's saint is someone else's Satan. More attention needs to be paid to the complexity of historical figures rather than sorting out who is good and who is bad by the arbitrary decisions of the current zeitgeist.

I think a much better compromise would be to have a 'States Day' - at a Federal level on a set date each year and that this could be interpreted by each State however they wished. Each state and/or town within a state could put forward a historical person they wished to be celebrated and their story could be disseminated across that day. These celebrated people could be Italians, indigenous people or whomever the State feels is worth celebrating free from Federal involvement. :o)