There are many varieties of English: American English, Canadian English, Australian English, Hiberno-English, Scottish English, etc, etc. With these varieties contrasting in terms of dialects, spelling, pronunciation, grammar, vocabulary (wee/small, ye/yous/you, amn’t/ain't, trunk/boot), idioms etc.
I'm wondering how diverse the various varieties of Spanish are, with differences in English varieties used as a benchmark. For example, would Spanish in the Basque Country differ from Spanish in Andalusia to the same extent as Hiberno-English would differ from Cockney English? or are the differences greater or fewer. Would someone from Spain struggle to understand someone from Costa Rica?, in the same way that an American might struggle to understand a Glaswegian. Which two dialects are most similar: Castilian, Argentinian or Mexican?
Is there a dialect in Spain which is more similar to those spoken in Latin America?
Does Latin America have an upperclass Spanish dialect more similar to that spoken in Madrid?
What broad dialect families would you divide Spanish into? If so, is it very similar?
I do not speak Spanish, so don't go into the nitty gritty in your answer as I'm only trying to get a general picture. I am also only interested in spoken Spanish.