Just because you might drop a few bucks on the table after eating dinner in the States doesn’t mean that’s appropriate behavior everywhere. It’s best to check local customs before deciding to do the same in another country.
Some countries, such as New Zealand, Australia and Japan, don’t customarily tip and the result can be confusion for your servers. In other countries, such as France, the tip is added to the bill automatically.
Take the time and check online or ask locally if tips are customary before making the gesture.