A question for the americans

"Who discovered America?"

Of course, Native Americans crossed over into North America (from Siberia) tens of thousands of years ago - but they're rarely mentioned except on Thanksgiving. 

• Christopher Columbus (from Spain) in 1492 discovered some of the Caribbean islands such as Hispaniola.

• There is John Cabot (from Italy) who discovered the east coast of America.

• Vikings under Leif Ericson (from Norway) were probably in newfoundland around 1000 A D.

Modern Sweden started out of the Kalmar Union formed in 1397. The earliest images of petroglyph's can however be found in the province of Jämtland, dating from 5000 BC.

Scania, where I'm from, became Swedish 1679.
Before that, we belonged to Denmark.

"The area today known as Denmark has been inhabited by humans since the end of the last ice age, about 12,000 years ago. The Danes were first documented in written sources around 500 AD, including in the writings of Jordanes and Procopius. With the Christianization of the Danes c. 960 AD, it is clear that there existed a kingship in Scandinavia which controlled roughly the current Danish territory. Queen Margrethe II can trace her lineage back to the Viking kings Gorm the Old and Harald Bluetooth from this time, making the Danish Royal Family the oldest in Europe."



I got so curious to why many Americans consider themselves to be better than many Europeans when their ancestors were from Europe?
Is there somebody who can explain to as why that is?
Is it because of the world wars? Cause I don't get it.