To all non-US citizens, that have an LLC in US: • How do you manage your fiscal obligations? Like IRS forms and stuff... I'm concerned about dates • How do you handle book-keeping? Do you hire someone, use Xero or other software?

A bit late for an answer, but all the folks I know who have done this hire a bookkeeper / account who handles this form them, unless they get big enough to hire someone "local" to manage this (which often just means the local person works with the accountant). The most common software involved is quickbooks... not because it is good, but because it is ubiquitous. ISTR I might have used Xero at one point, and it has an integration with quickbooks. most things do.