If you are a foreigner I imagine your accent can give you away pretty quickly. Europeans would be far less likely to tip (or tip generously).
Source: I waited tables in NYC in a past life.
Before they got state drivers licenses, they could only show their non-US ID/passport whenever they got carded for alcohol. A few times, the venue would just tack on a 20% service fee.
One time, they asked the table next to them if they also got a service fee: They didn't. They complained, got the service fee waived, then told them to forget about getting a tip at all.
You might guess a person might be a non-tipper, but giving shitty service or forcing a discriminatory service fee will make that a self-fulfilling prophecy.
Southern europeans tip, there wouldn't be much difference there
Northern ones it depends, they don't tip at home but they usually do on vacations to southern europe (where tipping culture very much exists). Though some of that also has to do with currency conversions, at least historically, even if the tradition has stuck past the euro being introduced. So maybe that's why they don't tip when it comes to dollars?
No we don't. In Portugal, Spain, and Italy it's not common nor expected.