Antagonism is the very foundation of Islam. Muhammed wanted a religion that could compete with Christianity and Judaism as a means to recruit troops for his Jihads. Its purpose was to conquer land by way of exterminating other religions. So hatred of other religions is a staple of what Islam is all about.
What “international agreements”? That between, say, Turkey and Iran? Neither one wants the existence of the Israeli nation at all, certainly something that Israel would never agree to.
The United States is free to designate its primary embassy in whatever city within the territory of the country with whom they wish to establish diplomatic relations, but out of courtesy, this is most often in the designated capital city.
By way of illustration, Bonn was the acting capital of the country established as “West Germany” in 1955, but for diplomatic reasons an outpost was maintained in Berlin, even though it lay in disputed territory. Berlin was always the designated capital city of West Germany.