Plural of nationalities

Some that come to mind are the English, the French, the Swiss, the Dutch, the Irish.

Yes, those are good examples, but what about American, you say Americans, Canada, you say Canadians, is there like a rule to be followed in order not to make mistakesor it's just a matter of common sense?

I'm not aware of any rule.

If you wanna say or mention a number of people from France for example, you say:

two French? two French people?

I would tend to say, "two French-, Irish-, English-, Dutch-, Swiss-, etc. people".

Thanks for you help and if you gte to know smething like a rule I will appreciate that you let me know. Thanks again.