The country is not known as Czechia by English speakers anywhere I know of, and I've been living in and visiting English speaking countries and reading English for over 50 years. We know it as Czech Republic or maybe as Czechoslovakia if we are old and stubborn. Did it change name very recently?
Kinda, yeah :)
"On 14 April 2016, leading Czech politicians voted to register "Czechia" as the official English-language short name at the United Nations."
"Czech leaders insist that the country’s full official name is not changing: they are merely requesting that the United Nations register Czechia as an official shortened name (like “Russia” for “the Russian Federation”)."
"Czechoslovakia was a sovereign state in Central Europe that existed from October 1918, when it declared its independence from the Austro-Hungarian Empire, until its peaceful dissolution into the Czech Republic and Slovakia on 1 January 1993."
Technically yes. Interestingly, it's a very recent thing; it was largely pushed by the Czech government in 2016, and has been slowly gaining more widespread use since then.
My Skoda car proudly proclaims itself to be made in Czechia, and a number of UK newspaper style guides have been updated to use it. The EU also uses it in English language publications too.
Wikipedia has an interesting article on it: https://en.m.wikipedia.org/wiki/Name_of_the_Czech_Republic
No, the French letter R is a uvular trill, which means that it's pronounced by vibrating your tongue against your uvula. The letter hx is pronounced like the ch in the Scottish pronunciation of "loch." You should also be familiar with it from German. It is a difficult sound for English speakers.
You must have your tongue where you have saying 'g' letter. But you say "h". If you want to say h (not ĥ) you must have your tongue at bottom (as in 'e' letter). I am talking about esperanto 'g' and 'e' letters.
I guess that it's used mainly for the ĥ character and sound which (as I understand) is has disappearing from Esperanto because it's hard to pronounce for way too many people. In any case, you're at least aware that such a country exist and you probably know some Czechs which is probably more than most Czechs know about individual US states :-).
Actually noone cares about states inside one country. How many states do you know from Mexico, Canada, Germany or Russia. Not much? Well, me neither. Though, I think when someone says: "Oh, I don't know that the Czech Republic exists," the best answer is not: "Don't worry mate, I'm sure Czechs are not aware about US individual states as well."
I think you misread both @donaldo_zouras' and my comments. He said that he's only vaguely aware of the existence of Czech Republic not that he didn't know it existed at all.
I replied that it's not bad considering that it is a small country (around 11M people ~ roughly 1/70 of Europe, 1/50 of the EU, 1/320 of the USA) with a second grade role in European politics and even smaller in the world politics. It's most notable export are Škodas (owned by German Volkswagen) and beer (maybe the long lasting legal battle between Budweiser and Budweiser might ring a bell) which (I assume) don't make it to the USA. An American will most likely know some Czech athletes (esp. ice hockey players like Jágr, Hašek), maybe a few filmmakers (Miloš Forman), possibly authors (Seifert, Kafka) - it all depends on one's interests.
Let's be realistic, without a specific interest or some family tie, there's really no reason an average American would know anything about Czech Republic. Of course, it might warm our hearts in an absurd surge of nationalistic pride (= an absurd appropriation of accomplishments of people who happened to be born/live in the same arbitrarily delimited country or one of its predecessor) if he did. Also the same knowledge expressed by a Slovak would be a sign of ignorance.