My preference is to use U.S. formats, measurements, currency for U.S. articles, and take it from there: use the forms appropriate to the subject. If there's no obvious default, then leave it alone, following the BC/BCE wars that spawned the Arbcoms's Jguk decision.
ARBCOM hasn't made a decision yet afaik, they only placed a halt on automated changing the date formating articles (eg: via bots and scripts).