Consider these possibilities:

• USA is considerably new country and built with no distinctive, coherent ancient history and mythology. As such, its people often grab every opportunity to produce a mythology they can consider their own. It makes them perceive as unnatural/supernatural things we, citizens of old world rationalize, or brush off as of little value.
• USA is an experiment by whatever the "aliens" are, so it's natural for them to supervise it with more interest than the rest of the world.
• There are no aliens, it's just USA itself testing new technologies of theirs.
• Other superpowers are very secretive by default and they simply hush-hush every sighting they can.

Because the major export product of the United States is American culture. UFO/alien abduction/government cover-ups are kinda baked into American popular culture at this point. Just the idea that the government is simultaneously incompetent yet able to successfully hide far reaching evidence of alien visitation is as American as baseball and apple pie.

I've no doubt people are looking up at the night sky all over the world and seeing things that they think are possibly alien craft. I've also no doubt that there are stories and folklore about abductions in every country on earth. But American culture is insidious and infects just about everything. This forces every other event to be reframed in reference to the American UFO phenomenon.

Schizos, opioids, conspiracy nutjobs, lead poisoning and low education multiplied by spiritual bankruptcy. Deny it all you want, Yanks, but it's true.

Because most of the crazy lunatics are in the US?

The real answer is that it doesn't; you simply hear about it more. The other superpowers who are flying super-sonic jets around all day are much more secretive and if you think the retribution is bad here let me tell you it is worse in China or Russia. Also, people see these things with their naked eye all the time. Seriously, drive out to the mid-west and just look at the sky at night. You will see them up there, making their 90 degree turns and all. But the stigma is really so bad within our culture that people just don't talk about it, and light pollution is so bad in the cities that you can't see the sky anywhere near one.

The short answer is that it doesn't. I think some of the most compelling cases I've seen have come out of South America, east Asia, and Europe.

The long answer (is really just speculation on my part) the US dumps so much money into defense that the citizens don't have healthcare, education, or decent social services. The USA is the richest nation on earth and many billions of dollars spent on defense are classified or unaccounted for. It seems likely to me that the US is one of the only nations with a program in place to study any recovered craft so any of our allies would likely send materials/craft to the US to be studied.

Usa's society is very susceptible to conspiracy theories in general, and the UFO story is one. The question, whether there are actually aliens or not, steps back behind the conspiracy accusation against government/secret services/etc.

It's a combination of the US being a large country, and being full of idiots and quacks.

Possibly because the US defense industry dwarfs the rest of the world and is constantly testing new technology that can be confused for UFOs. Russia and China, while also having large defense industries, are nowhere near what the US spends.

Well...

If you think about it...

You hardly ever see any news from Russia or China... mostly because you don't frequent Russia or China based websites.

Also, turns out, their news generally isn't in English, except for propaganda

1. Area 51 - a real USAF research facility where cutting edge aircraft were tested in the mid 20th century. People in the area truly did see Unidentified Flying Objects, in the sense that they saw aircraft the likes of which they had until then believed were impossible.
2. https://en.wikipedia.org/wiki/Bob_Lazar who single-handedly reinvigorated the UFO conspiracy theories long after Area 51 had concluded most of its Cold War era secret tests.

If you pull back all the layers of this onion you will most likely find out its just humans manipulating a situation to fund secret projects and funnel money into private corporations. It happens elsewhere as well but mostly under other different veils.

UFOlogy is huge in Brazil. They have a lot of famous “incidents”, google Varginha alien and you’ll see what I mean.

I’m not a believer at all, I just happen to know about it cause I lived there for a while and one of my coworkers was a UFO nut.

My theory... Lead pipes and general high level of heavy metals in the environment, especially in the areas many of these sightings happen in...

Or idk aliens maybe...

It's a cultural thing? Maybe there are a disproportionate number of alien believers in the US so they are more likely to attribute odd sightings to aliens.

You watch movies made in the us

Because the USA is the true center of the universe. Duh./s

You know why. It requires stupid people.

Primary stargate is in Colorado so that's where the Goa'uld would strike first

Where I live, people believe supernatural stuff more than UFO stuff. So when they see something weird, the first thing in their mind would be ghosts instead of aliens.

Because it’s propaganda created by the US government. You should be asking yourself why is the government working so hard to distract you? What are they trying to hide? It’s not aliens I can promise you that much.

Also ask yourself this. If there is so much discussion and attention to aliens then why is it there is always zero evidence? Absolutely no evidence other then some strangers word.

Because it has become an almost normal thing now to assume alien ufos and conspiracies are real in the US. Reports of UFOs though have gone down since everyone has a phone camera though. You don't just have a single guy making a shitty 8mm film of a grainy blob of light.

Russia has a lot of mystical and conspiracy beliefs too. Likely a result of their history of authoritarian govs and religious beliefs.

We don't have fae shit in the US

The rest of the world is just jealous of our alien friends that sell us advanced aircraft in exchange for drugs from Mexico and Columbia.

One of the biggest events was in Varginha, Brazil.

There's also the fact that mainstream news in most countries consist of 50% local and 50% US news.

I think its simply because we have a larger active military along with a freer media/speech. When you constantly have military jets in the air, ships on the sea, and satellites in space the chances of catching edge cases is just higher.