The best way would be to contract them or go through an agency like Manpower that actually already have offices in the country where your artists live.
The reasons for that are not just the tax situation but also labor laws:
Now if you subcontract you will have no issue with taxes and all you will need to provide them would be a 1099 at the end of the year.
I'm pretty sure the answer is simple: you cannot hire them. If the Europeans don't have a US citizenship/green card, or otherwise eligible to work in the US - you cannot hire them as employees.
You're not required to verify employment eligibility for contractors, but knowingly employing illegal immigrants (i.e.: aliens not eligible for employment) is IMHO a Federal offense. If they're in Europe - then you can definitely contract them.