今までの経験などについて問うときは過去形のvisitedやdid you visitではなく、現在完了形のhave you visitedを使います。
「今まで行った国の中で一番良かった国はどこですか？」
Of all the countries you have visited, which is your favorite?
「それはどうしてですか」
Why?
Why is that?
The phrase "been to" and "traveled to" are interchangeable with the word "visited". They all mean the same thing which is arrival at the designated location. "How many countries have you been to" is the most common form of dialect when communicating and asking another fellow passengers about the number of countries he/she has been to, and it is a a very common way to express this message.
"been to" と "traveled to" は "visited" と置き換えることができます。これらは全て同じ意味で、ある場所に到着することを表します。
"How many countries have you been to?"（今までに何カ国に行ったことがありますか）は、今までに何カ国に行ったことがあるか尋ねる一般的な言い方です。
"How many countries have you visited, to date?"
How many - what is the number
Visited - to stay in for a short period of time. You could also ask (How many countries have you lived in, to date. - Meaning you stayed for longer than a month in the country.)
To date, meaning up to this point in time, to this day, etc.
This is a good expression to use when you first meet someone or to ask a friend who is an avid traveler.
"How many countries have you visited, to date?"（今までに何カ国旅行に行きましたか）
How many - どのくらいの数
Visited - 短い間とどまること。一カ月以上の長い滞在なら、"How many countries have you lived in, to date?"（今までに何カ国に住んだことがありますか）と聞けます。
To date - 今までに、今日までに、など
初めて会った人や旅行好きの友人に対してこの質問をすると良いと思います。
"How many countries have you visited?"
This question is asking an individual(s) how many countries they have visited, how many countries they have been too. to 'visit' somewhere is often used to describe site seeing/being a tourist.
"How many countries have you traveled?"
Again this asks how many countries someone has visited, by asking where you have traveled is the same as asking where have you visited/been too/seen.
"How many countries have you visited?"（今までに何カ国を訪れましたか）
「今までに何カ国を訪れましたか」と尋ねています。'visit' はしばしば、観光でどこかを訪れることを表します。
"How many countries have you traveled?"（今までに何カ国を訪れましたか）
こちらも同様に、「今までに何カ国を訪れましたか」と尋ねています。
'traveled' はここでは 'visited/been to/seen'（訪れる／行く／見る）の意味です。
When you want to ask someone how many countries they have visited until now; then you may ask in the following ways:
-How many countries, in total, have you visited?
-How many countries have you visited?
今までに何カ国に行ったことがあるか質問したいなら、次のように言えます。
-How many countries, in total, have you visited?（今までに全部で何カ国に行きましたか）
-How many countries have you visited?（何カ国に行ったことがありますか）
アメリカ合衆国 
インド 
カナダ 
イギリス 
南アフリカ 
