Alright, part 1 of my resolution. I'm going to do this in alphabetical order and by continent.
I'm also going to hurry with these, lest I end up in the middle of learning about South Korea when it suddenly becomes Unified Korea and even more suddenly becomes The East Asian Radioactive Zone of Exclusion.
Accounting for European Colonialism and contemporary politics, many of the facts I am about to detail may predate the existence of the modern nation they relate to.
Antigua and Barbuda: Admiral Nelson was not fond of Antigua. His time stationed there was filled with illness, mosquitoes, and enforcing trade embargoes against the United States. This last factor made him very unpopular among Caribbean traders.
Bahamas: The original inhabitants of the Bahamas were the Lucayans. Sadly, the Atlantic Exchange was unkind to them. A combination of disease and Christopher Columbus's colonial practices wiped them out.
Barbados: European colonists found Barbados mostly uninhabited. Long before their arrival, it had been occupied and fought over by a few First Nation communities, but it seems they moved on to other things before the Europeans arrived.
Belize: As of January, 2018, Belize is in the middle of a decades-old territorial dispute with Guatemala. Belize stands to lose more than half of its area, should Guatemala's claim be enforced and upheld.
Canada: Well, offhand, I can say that Canada kicked the US's ass in the War of 1812. More often than not, wars like this result in tensions and violence between two communities in perpetuity. For the US and Canada, however, their relationship has been amicable ever since.
Costa Rica: Archaeological evidence indicates the presence of a material-rich civilization in Costa Rica that pre-dated the coming of the Europeans by hundreds of years. It seems the exact history of Costa Rica's native jade-work and goldsmithing has been lost. While the Europeans weren't solely responsible for this obfuscation, they sure didn't help.
Cuba: I pretty much have to make this one about Fidel Castro. He was an absolute Villain, but also a badass. The Cuban Government estimates 638 failed assassination attempts were made on Castro, both physical and character. This number is difficult to verify (or narrow down based on various criteria), but this number is also generally accepted.