Dar al-harb means a country that is not under the domination of Islam. In that case, America is dar al-harb.
According to Imam Abu Hanifa and Imam Muhammad, a Muslim will not be regarded as a sinner if he receives interest from non-Muslims and if he gambles when he is sure that he will win. However, according to Abu Yusuf, it is haram
If a person makes a transaction with interest in dar al-harb, it is permissible according to Imam Abu Hanifa and Imam Muhammad. There is no drawback to a Muslim living in dar al-harb receiving interest from non-Muslims. For, receiving interest is not regarded as treason according to them; it is normal. (see Halil GÜNENÇ, Günümüz Meselelerine Fetvalar)
Betting bilaterally and doing similar things are regarded as gambling. For instance, before two people races if one of them says, “If you outrun me, I will give you such and such amount of money; if I outrun you, you will give me such and such amount of money”, such a bet is regarded as gambling.
However, if the bet is unilateral, it is permissible. That is, if one of them says,” If you outrun me, I will give you such and such amount of money but if I outrun you, do not give me anything”, such a bet is legitimate. The person who obtains such money can use it.
It is not permissible to arrange a match or a game by laying some conditions and to take the prize given as a result of the match or game. Such a practice is regarded as gambling.
It is understood from the resources given that this statement is a hadith.
Harmful games are the games that were prohibited by the religion like gambling, tatayyur (regarding things as ominous) and games of luck. Something forbidden is involved or is possible to be involved in them. In fact, all of the permissible games become harmful and forbidden when they are transformed into that form.
It is necessary to protect children from forbidden games and games that are like them.
"Everything that Allah prohibits is a major sin, even a child’s gambling." (Kütüb-ü Sitte, Volume: VIII, Çocukların Oyunu)
Thus, the Prophet lays the responsibility of the child in gambling on his parents.
Among those games, there are some games that were known at that time and that were prohibited. One of them is backgammon. The Prophet (pbuh) said,
"A person who plays backgammon is regarded to have disobeyed Allah." (Abu Dawud, Adab, 56; Ibn Majah, Adab, 43; Muwatta, Ruya, 6)
As a matter of fact, in the narration that you quoted and in another narration in Muslim, it is stated that playing backgammon is haram as follows: "He who plays backgammon is regarded to have put his hand in the blood of pig." According to the narration of Nafi, "Ibn Umar would beat the members of his family who played backgammon and broke the game board into pieces."
