Polo + Lando = Pololando. But if you are connecting roots, you can miss 'o' letter if you don't have problems to speech (So Pollando and Pololando should be correct). And I forgot. Esperanto words you must read as you write, so Pollando, not Polando. And Kio as Ki-o, not Kjo.
Teĥnically there is and it means the same.
When combining two words by joining them together (compounding), one can (but doesn't have to) omit the grammatical ending (speech marker, desinence) of the first one, when it wouldn't make the word unpronounceable. However, there are no strict rules as for what makes a word unpronounceable so it is up to the speaker to decide. Also, when the choice of the grammatical affiliation of the first word wouldn't change the meaning of the compound, one uses the one with the noun modifier.
So if you want to say “eating time, mealtime” you take the words manĝi and horo and combine them into manĝhoro and if you find it hard to pronounce you can go with equally correct manĝohoro (since it means the same as another, theoretical variant manĝihoro).
As for the pronounceability: When the second word begins with a vowel or the root of the first one ends with a vowel, tradition of Esperanto describes these compounds as pronounceable and no marking is used. There are also many compounds which are thought traditionally to be unpronounceable without a desinence (noktomezo, fingromontri or vivovespero) or pronounceable without any desinence (vaporŝipo, jarcento or Pollando) but in the end, the decision is up to the one oneself.
Most American place names that are not either American Indian words or Latin neologisms are simply European place names, sometimes with the word "New" in front of them. Some of them are quite charming, my favorite being Hindoostan, Indiana. Of course, many would find the name of my birthplace, Olympia, Washington, pretty silly.
There are more Polands! :) https://en.wikipedia.org/wiki/Poland_(disambiguation)
Both (Polio and Pollando) are correct. Also Polujo or Pololando. But the Pollando is used more times.
The affix °-i- used to create country names is NOT OFFICIAL and therefore not commonly accepted. One argument against it (other that the main, that there already is unambiguous -uj- affix) is that already many words end with letters -io and using it to create country names makes the language confusing and some names offensive (exactly like that terrible °Polio).
I'm proud citizen of Pollando (or Polujo) and I ain't no Heine–Medin disease!
Many people nowadays use the °-i- affix to create country names, but bear in mind that it is NOT OFFICIAL and many people have pretty good reasons to advocate against using it: it creates some homophones (not all of them fortunate) and a big confusion with the country names which are not national-based (like Ĉili·o). If you want to know more, check the book Rusoj loĝas en Rusujo.
But to answer your question: when creating country name from the word of nationality one can use -uj- or -land- affixes and there's no difference in meaning, so teĥnically you could use any of these two. However, normally one uses -uj- (like in Aŭstr·uj·o, Ĉeĥ·uj·o, German·uj·o, Hispan·uj·o, Kazaĥ·uj·o or Rus·uj·o) and the tradition of Esperanto (and the Akademio de Esperanto) recommends using -land- specifically to six countries: Finn·land·o, Pol·land·o, Skot·land·o, Svazi·land·o, Svis·land·o and Taj·land·o.
Places named after its inhabiting nation/people can either use the suffix -uj- (or the later introduced suffix -i-), or be formed as a compound with land- (meaning ‘country’). Both ways are technically correct, but traditionally places tend to be called almost exclusively using only one of those methods.
Most of them use the suffix (the traditional -uj- or the newer -i-), but for example in the case of Skot·land·o, Pol·land·o and Taj·land·o, the land- form is predominant and recommended.
So although you would be understood, saying Pol·uj·o would raise some eyebrows. Saying Pol·i·o would raise even more of them, since polio- is also the medical prefix used in names of illnesses of the grey matter (e.g. in poliomjelito, ‘poliomyelitis’, commonly referred to in English simply as ‘polio’).