What is the first known instance of gift-giving backfiring across cultures?

An incident leading to the First Opium War comes to mind.

The setting is China in the late 1700s. European traders want free trade with China, but China has restricted them to a single port: Canton. Long story short, the British wanted Chinese tea, lots and lots of tea! This meant a lot of British hard currency was going to China in exchange for their tea. The British wanted to trade opium from India to get some of that currency back and redress their trade imbalance. The Chinese, understandably, did not want to be flooded with British drugs.

In 1793 the 1st Earl of McCartney sailed to China as official envoys of the King bearing gifts and wishing to negotiate a trade agreement and open an embassy. The Chinese felt that no one was equal to their Emperor, especially not some western barbarian; rather than seeing this as a trade mission between equal monarchs, they viewed it as a mission of tribute from the British King to the Emperor. And the cultural misunderstandings and hubris roll on from there.

The British requested to land at Tianjin near the capital, more convenient to deliver their gifts and negotiate with the Emperor. The Chinese considered it an affront for a tributary mission to decide where it should land. The British noted their gifts might be damaged by a long overland journey, so the Chinese relented.

Once McCartney finally met with Emperor Qianlong, there was a complicated issue of protocol, particularly with the kowtow. It was required that in the presents of the Emperor, or receiving his edicts, you kneel with both knees on the ground and bend over to touch your forehead to the ground. The British considered this humiliating, their monarch was the most divine, powerful, and civilized, and if they didn't kowtow to him, they weren't going to kowtow to the Emperor. The Chinese, of course, found it insulting that this western barbarian did not kowtow to their most divine, powerful, and civilized Emperor. In the end, McCartney genuflected as he would to his King.

When the gifts were presented, more confusion. McCartney had brought marvels of British science, demonstrating the value of trade between Britain and China. The Chinese court was confused, wasn't this was a tribute mission? These gifts didn't seem like tribute. So they were sent away with no issues resolved.

Emperor Qianlong, wanting to let King George down easy, penned him the most amazing and (probably) unintentionally snarky letter that demonstrates all the cultural misunderstandings between China and Britain. Here's some highlights chosen by Extra History.

You, O King, live beyond the confines of many seas, nevertheless, impelled by your humble desire to partake of the benefits of our civilization, you have dispatched a mission respectfully bearing your memorial. Your Envoy has crossed the seas and paid his respects at my Court on the anniversary of my birthday. To show your devotion, you have also sent offerings of your country's produce.

I have perused your memorial: the earnest terms in which it is couched reveal a respectful humility on your part, which is highly praiseworthy. In consideration of the fact that your Ambassador and his deputy have come a long way with your memorial and tribute, I have shown them high favor and have allowed them to be introduced to my presence. To manifest my indulgence, I have entertained them at a banquet and made them numerous gifts. I have also caused presents to be forwarded to the Naval Commander and six hundred of his officers and men, although they did not come to Peking, so that they too may share in my all-embracing kindness.

...

If you assert that your reverence for Our Celestial dynasty fills you with a desire to acquire our civilization, our ceremonies and code of laws differ eso completely from your own that, even if your Envoy were able to acquire the rudiments of our civilization, you could not possibly transplant our manners and customs to your alien soil. Therefore, however adept the Envoy might become, nothing would be gained thereby.

Swaying the wide word, I have but one aim in view, namely, to maintain a perfect governance and to fulfill the duties of the State: strange and costly objects do not interest me. If I have commanded that the tribute offerings sent by you, O King, are to be accepted, this was solely in consideration for the spirit which prompted you to dispatch them from afar. Our dynasty's majestic virtue has penetrated unto every country under Heaven, and Kings of all nations have offered costly tribute by land and sea. As your Ambassador can see for himself, we possess all things. I set no value on objects strange or ingenious, and I have no use for your country's manufactures.

...

It behooves you, O King, to respect my sentiments and to display even greater devotion and loyalty in the future, so that, by perpetual submission to our Throne, you may secure peace and prosperity for your country hereafter.

It's worth reading in full, and goes on to give their reasons for rejecting the British proposals.

For more about this, watch Extra History's series on the First Opium War.