I was wondering if I can fly into San Francisco (SFO) or Los Angeles (LAX) airport directly from Asia (or Europe) and get my TN stamp at the airport.

Yes, LAX and SFO process TN NAFTA Visas if this is your first Port of Entry. Usually there is an Immigration Officer knowledgeable about TN visas on duty. Try to schedule a flight that arrives into the U.S. during regular business hours so the chances of an Immigration Officer with TN NAFTA visa experience being available is more likely.