20% is not the normal minimum in the US.

Edit: here are some supporting links.

15-20% suggested with 20%+ recognized as a minority opinion and for extra good service: http://www.cnn.com/2015/03/02/travel/experts-guide-to-tippin...

The highest tipping state averages 17% and the lowest averages 15%: https://qz.com/189458/the-united-states-of-tipping/

Agreed; 15% here in Canada is considered normal/polite/nice, but I also believe our wages for service workers are higher. The USA "$2.13/hour for tipped worker" feels like both business AND government forcing you to pay employee wages...

Canada minimum wage: https://www.labour.gov.on.ca/english/es/pubs/guide/minwage.p...

Liquor Servers Minimum Wage $9.90/hour

Some people have been claiming that 20% is normal for the US. But many people believe 15%. There are even some people who claim that 25% should be the norm.

You can definitely get away with 15% at places where you don't regularly eat. I do 20% at regular places where the waiter will remember me for sure and I don't want them to get the idea that I don't like them.