I am Italian and whenever I go to Spain I usually don't really need to speak English because the languages are close enough that you can go by by just knowing a handful of basic words (and the Spaniards I meet usually prefer it that way). This is both a blessing and a curse; all Italians I met living in Spain (and viceversa, all Spanish-speakers I met in Italy) tend to have a hard time learning the other language "properly" because the threshold for being understood is extremely low. If, perchance, someone speaks an Italian with Spanish grammar, people will still understand you perfectly.

Given that Castillan and Portuguese are even closer (both Western Romance, part of a linguistic continuum, ...) I find it very hard to believe that honestly. I am only familiar with the European variants, thought. Maybe the issues you faced are due to how the Latin American variants have diverged significantly over the years?