Why are most successful web startup from the US? What are the factors?

I am not from the US, so this is a outside view, which may be biased:

• entrepeneur mentality
• attracts the best minds from other countries
• existing channels to get funding from private investors
• excellent universities, which often also facilitate startups
• wealthy population (at least in terms of spending)

1) US is the largest & fairly homogeneous market in the world = w/ 310+million people - you only need a tiny fraction to "get traction"

2) Advertisers here pay the most of eyeballs, so much easier to monetize free or "freemium" websites

3) Very low barriers to entry in terms of admin/government intervention, especially at the web-startup phase

It's worth remembering the USA has a large population and if you were to actually look at startups per head it's not massively different from that of Western Europe.

What makes US slightly different is that their is much more opportunity for investment and funding then in Europe and not just from big names. VC funding is found across the globe but the way tax and other conditions work means you will find the concept of Angel Investment is much more prevalent in the US then in say the UK. Coupled with a university system that allows innovation and IP control to students.

Add to this a powerful technology media and sheer numbers you end up with a scenario where startups can be given a large amount of money and exposure very quickly. This doesn't mean that startups are not successful in other countries far from it. One worrying trend is the idea that people have to be in Silicon Valley to "make it" it's certainly "a place" to be if funding is your primary aim but it's not a prerequisite to succeed.

Singapore have been named the most start-up friendly country in the world several years in a row.

You can easily "replicate" as you put it, the conditions US start-ups have. The main factor behind those highly successful web-based companies you mention is they have received a huge financial backing through funding.

Now the core shared factor of the companies you mention is they target a very broad audience, which have nothing to do with their success but rather have been a reason behind them getting the funding they needed to grow, when they started attract attention from investors.

It's a global market, saying that the US population have something to do with the companies success I believe is invalid. Anybody can target the US market no matter what country they reside in.

What makes the US stand-out with their web start-ups is they do have a large amount of big funding companies and of cause because the US have a huge population it of cause means even with a small success-rate for their businesses there will be some big success stories.

If you do a little digging you'll find there's a lot of big web-based companies residing in Singapore and many means to get help and advice as a start-up.

As well as investment culture I think the size of the home market is a factor. Companies usually target their home market first and if it is the US rather than Belgium by the time you are doing well in it you have reached a considerably bigger scale, that gives you a better chance to be successful on the global stage.