Spain is a major part of the EU.
There are also a great many British Ex-pats in who retire in Spain, not to mention that Spain is a favourite holiday spot.
Milton Friedmen convers it pretty well in https://www.youtube.com/watch?v=3eyJIbSgdSE. It's an old problem :/
It's "mañana", by the way. You wrote "español" so you clearly have access to ñ.
But basically, the joke is that Mañana never comes. Anyone familiar with (remote) Island life, from Islay on the west coast of Scotland to Saltspring Island on the west coast of BC will surely identify.
Many countries view hard workers working through the daylight and having evenings / night to themselves. However in the hotter nations the middle of the day and afternoon is often taken off, and work restarts later going into the evening/night. Thus it often appears like these countries only work half days.
The truth is now common knowledge around Europe however the traditional image of a Spaniard asleep in the middle of the day persists alongside the camp French snob and the Tea Toting and Tutting Brit.
As I see it the joke is no more racist than joking that the US brings kilotons of freedom to the world or that Canadians are sorry.