Two things: First, Jonah asks, "Was not this my saying?" and though I realize he's asking rhetorically, actually this wasn't his saying -- actually he didn't say jack, he just up and ran to Joppa to get on a boat for Tarshish. Maybe what Jonah means is that this is what he was thinking; presumably the words are interchangeable when your interlocutor is God. The other possible interpretation is that Jonah is just making stuff up, possibly because his real reason for running away was that he was afraid for his personal safety (always a legitimate concern for prophets). But I'm guessing that he's telling the truth here, more or less, and his hatred for the Assyrians was his primary reason for defying God. Probably the contemporary reader of this story (or hearer; I think it wasn't written down for quite a while) didn't need this motivation spelled out. I mean, who wouldn't go to any lengths to guarantee the destruction of Nineveh? To most modern readers, though, this is a bit of a revelation. Maybe, because this is a Bible story, the reader who doesn't know much about Assyrian history has no clear idea of Jonah's motivation up until this point; in stories with morals, it's the behavior necessitating the moral that's important, not so much the reason for the behavior necessitating the moral.
Second thing: The author, or possibly the translators of the King James Version of the Bible, really like the word exceeding, which appears five times in the Book of Jonah. It is a story about big things. The storm is exceeding, Nineveh is exceeding, Jonah's fury is exceeding. This is part of what makes it funny, the sheer enormity of every element.
I lied, three things. "When I was yet in my country" was poignant then and it's still poignant now, though the contemporary reader (or hearer) may have been thinking specifically of the Assyrian habit of moving conquered peoples around forcibly. This is how the Ten Lost Tribes got lost. The Neo-Assyrian Empire had a policy of moving troublesome populations into areas where they'd be considerably outnumbered by people of other nationalities; this had the effect, in the short term, of neutralizing their identities and making them less likely to try to do things like foment revolution. It's hard to foment revolution when you speak Hebrew and everyone around you speaks Akkadian, I guess. In the long term, though, this turned out not to be such an effective policy, because if you do it too much those minority populations start getting bigger and bigger. Anyway, to the subjugated peoples near them, otherwise known as "the peoples near them," Assyria meant exile, that word that looms so large in Jewish history. "My country," cries Jonah -- my people, my God, these things are Hebrew, I am Hebrew, can nothing be kept from the Assyrians? You're supposed to be for me, how can you be for them too?
I like that the God of the Hebrew Bible invites argument. I like that his favorite people are the ones like Moses and Job who really unleash their anger on him. Jonah's not going to get what he wants, but God really loves him. And what's perhaps just as important, God really wants him to understand.