There are some internationally recognized standards what constitutes a democracy, and the USA fits some and not others. For example, the USA wouldn't meet the criteria for democracy to be considered for EU membership, in the unlikely event it would apply for that.
The main sticking point is that it practices capital punishment, together with countries such as People's Republic of China and a handful of African countries. Intralegal execution of minors being especially problematic. Several treaties on international criminal law concerning war crimes is not recognized and its citizens are unlikely to ever be subject to the Geneva convention.
The second important point is the lack of an independent legal system. High ranking judges gets hand picked by politicians, in a very literal way. (Which is something that has also has happened in for example Poland. This is widely regarded as a loop hole in the EU democratic criteria. A country could not have been considered for membership under those conditions, but there is no jurisdictional power against reneging on that policy post membership. Subsidies gets frozen, but that's about it.)
Recently, major changes of governmental policy that affect millions of people have been made by an unelected body of officials who have lifetime terms. You may have even seen it in the news.
While I would love to take that on I am genuinely puzzled by what you mean. “No one can question American democracy because they don’t have a better one?” Sorry but if that’s it that’s a dumb take.
I'm not sure it is as black and white as you suggest.
If you were to create a time machine and bring an ancient Athenian to the modern day US, the Athenian would not recognize the US system of government as, democracy. With the exception of jury trials and referendums, the demos do not directly engage in governance.
The US doesn't even allow the majority of the population to select those who perform the actual governing. E.g., a person from Wyoming has much more representation in the Senate than a person from California.
And, for the president, the population votes, but the winner of this election is not the one who got the most votes from the population, it is the one with the most electoral college votes. Again, the Wyoming voter gets more representation with one elector per less than 200K Wyoming residents, and only one elector for over 700K California residents. It is how the US got Bush "W" and Trump even though they both lost the vote of the demos.
With all the money in elections, even if there were majority representation, the US would still have moneyed interests dominating politics.
Some argue that the US is an oligarchy:
https://scholar.princeton.edu/sites/default/files/mgilens/fi...
