This sounds like American exceptionalism. I feel that both American and Britain are great countries. The Magna Carta, not the Declaration of Indpendence, was the first, tentative step towards defined citizen rights. Common law is very admirable. Other countries, though, clearly have better standards of living and more actual democracy and freedom. These countries are usually comprised of one culture, though. America is amazing in the way that it accomodates so many different cultures.
I could write an endless list of what is right in America.
My answer to your post would be two-fold. First, I am American. My personal interests are here. I want my country to be the best possible. Remarking about ugly facts from our history is not being unpatriotic. The past affects us. Second, when you claim to be .:Christian nation, the best nation on earth, all the lies they tell grade school children, rather than actual historical fact, the hypocrisy critique becomes heightened. Actual history is multi-layered and America is so much greater when viewed through these facts, rather than myths that non Americans find humorous. Another factor is that people should consider the culture of the time rather than exporting today's values on the post.
Thomas Jefferson, the main drafter of the Declaration of INdependence, ambassador to France, Secretary of State, and president, is the perfect example. "All men are created equal>" is a joke when viewed through the facts. Others, such as Washington also had slaves, Jefferson only freed his children when he was blackmailed by Sally Hemmings. He did not subscribe to any gentlemanly notions of slavery, which others such as Washington did. Washington and many others' private writings expressed grave moral doubts about slavery. Jefferson did not.
America has done many great things. We rarely are taught about them in school. Every culture believes its culture is the best.