There's a lot of differences between Spain and Latin America alone and then there's differences between Latin American countries themselves. A main difference between Spain and LA as a whole is pronunciation, the pronunciation is very different especially when it comes to words with "Z" in it. There's also a lot of different slang. A particularly egregious example is the word "coger". In Spain, "coger" is basically "to grab" while in Latin America it's basically "to have sex". We use words like "agarrar" in LA instead of "coger". You have to watch out for that one, seriously, unless you want people to think you like to have sex with everything! I don't know about French. I have a couple of Spanish-native friends who are studying French and find the grammar and pronunciation to be very different from Spanish. One pointed out that it was closer to English than Spanish. Portuguese is relatively easy for Spanish-natives to pick up, yeah. It has some sounds that Spanish doesn't but a lot of words are similar and mean the same. Italian is similar in this sense, too. I honestly think this makes it kinda harder to learn the language though, since you are thinking about its similarities to Spanish and end up getting screwed by false friends and such.