Is it considered Haram when someone ridicules a certain race or individuals from a particular country by using stereotypes like stating "people from X country are stingy"?
Yes it is a sinful act to say that.
Blaming all people from certain country or certain tribe or ethnicity etc is wrong. The person who says that will be doing injustice on all those people and he will face all of them in the Day of Judgement as a wrongdoer.
He will be responsible to compensate all of them till they agree or he will be punished.
Wassalam.