Ha ha, good luck finding a porter in Sweden, never seen one and I live there. I never tip taxis, taxi service in Sweden is one of the most expensive in the world. No need for a tip. Just swipe the credit card and sign.

10% on a restaurant seems ok if service was ok AND service charge is not already on the bill.

But as numerous posts already stated, US is not Europe or Asia. You do as the locals and tip where expected, otherwise, don't travel. I always give a daily tip to hotel maid in the US. Why? She handles my personal stuff and I want her to be happy and take care of me.