Just because you're adjacent to the AI doesn't mean they wish to expand your direction. The AI is sometimes fickle about what it considers it's "domain" or "sphere of influence".
Current game, Portugal and I are on opposites sides of a continent. Portugal conquered Korea and razed their city next to Fountain of Youth. They never resettled, so I sent a settler WAY over there and claimed it (playing Spain and I wanted my 20 Happiness). Portugal has never complained about border proximity or purchase of land tiles.... Arabia (over on my side of the continent) made a comment about where I chose to settle in lands that belonged to them...
Arabia also complained when I settled an island between Portugal and Austria (Austria being the closest part of second continent to the far side of my continent). If anyone has had rights to complain about where I chose to settle, it was Austria or Portugal... but neither considered my choices infringing on their domain.
Same goes for CS competition... I quickly allies the four CS closest to me. Never had complaints from neighboring civs, but when Carthage (from second continent) sailed by my lands, they turned around and said something to me about my relationship with Buenos Aires (which had been my ally since Ancient era, now it's Renaissance when Carthage met them) saying that it was within THEIR sphere of influence.... (times like these I wish I could suggest the AI leaders play a game of "hide and go **** yourself").