I want to take part in Iceland's long term remote worker visa to visit for 6 months
HR thinks this may be a tax liability, but the duration is explicitly less than long enough to be considered a tax resident
Is there an issue with the large corp having an office in Iceland or is HR being overly cautious?
(extra detail I don't think should matter: I'm Canadian, company is American)
Assuming your large corp / HR are friendly, they might even be willing to switch to a contractor relation (depending on the juristiction this might not be allowed, e.g. Germany is very tough on contractors as employees).
This prevents the biggest problem of large corporates. Being in the country with employees might make you a 'permanent establishment' and therefore liable for local tax law.
Worth looking into Estonia's e-residency program and suppliers like xolo.io (The leap product, not the Go product).