You need to be a little careful with these rankings, because they're subjective. Forbes, for instance, drastically prioritizes taxes for its rankings. The corporate tax rate in the US is higher than that of Ireland, and (as Forbes summary straightforwardly admits) that pushes the US down in the rankings.

For a startup, there are significantly more important factors to consider than the corporate tax rate, not least because most startups are managed to avoid taxable profits for the first several years of their existence (sometimes all the way up until IPO). For instance:

* The US offers at-will employment. Ireland, at the top of the list, has an Unfair Dismissal act that allows employees with a year of tenure to file claims not only if they're dismissed, but if they're "constructively" dismissed --- that is to say, if their role in the company is substantially altered in a way that allows them to claim that they're being "managed out" of the company. Constructive dismissal is a standard market clause for executives and acquirees in the US, but is certainly not a day-to-day feature of employment law.

* The World Bank Ease-of-doing-business index dings Ireland, putting them far below the US, for (among other things) the difficulty of enforcing contracts in Ireland; my tea-leaf-reading from the index's abstracted data is that you have a good certainty of enforcing a contract base in Ireland, but that the process is more time-consuming and expensive than in the US, which is ranked 50 places higher than Ireland (at #11 overall).

* Similarly, the World Bank dings Denmark (putting them 2 places below the US overall) because (among other things) it's significantly more difficult to incorporate in Denmark than in the US (where you can do it approximately as easily as ordering a non-one-click-compatible book from Amazon). Denmark also has mandatory severance of up to 6 months wages depending on tenure. 6 months wages isn't a big deal to any big company, but for a startup, it could change the calculus of when the company will need to shutter during a downswing to meet its legal obligations to employees; in the US, so long as you can make good on any current wages owed employees, you can run up until the last minute.

* Sweden, which Forbes ranks higher than the US, has intricate employment law rules that require not only a legally defensible just cause for termination, but also a good faith effort on the part of an employer to find another job for an employee even if just cause exists to fire them. Sweden also allows shareholders to personally sue directors in a variety of situations. There is no way Forbes actually believes Sweden is a better place to start a company than the US.

Here is a combination of factors that makes the US a good place to start a business:

* Extremely well-tested corporation law that makes the formation of a company, distribution of equity, resolution of disputes, and enforcement of ownership relatively predictable.

* Virtually no government interference with the formation of companies themselves, so that you could practically form a new LLC for every individual Github project you started, pay less for that than you would for hosting costs, and stand a very good chance of having those LLCs defend your interests in disputes.

* Multiple classes of corporation, convertible between each other, with some optimized for "click a button on a web page and create an LLC for my Github project", and others, not that much more expensive, that allow for multiple classes of shareholder, with the laws for those corporate forms predictable enough that hundreds of thousands of dollars of venture funding have become a standardized packaged product for promising startups (this is mind-boggling when you look at the societal infrastructure that enables it).

* A system of at-will employment that (for the most part) makes employment of workers almost risk free, so long as you don't play fast and loose with owed salary or tax withholdings.

* A tax system that is reasonably simple, not disastrously onerous, and in many ways optimized for entrepreneurs (for instance, the differing taxation schemes offered for salary versus distributions, or the ease of deducting business expenses).

* Extremely well-tested employment law that, among other things, makes it straightforward to retain 1099 contractors for one-off projects without risking their conversion into full-time employees with severance rights.

* One of the world's largest single borderless markets, such that you can start a company in Oregon and, with almost total certainty, be able to straightforwardly collect money for services (other than direct financial services, insurance, pharmaceuticals, and agriculture) from people in Florida.

* The host of the world's largest equities markets, so that investors in startups can plow money into companies knowing that if that company is the 1 in 20 that is going to go public, the most lucrative place for it to go public is the country of its origin.

The US is probably not the best place in the world to start a company. Forbes and the World Bank agree that Hong Kong and New Zealand are better. But running a company in New Zealand also requires you to domicile in New Zealand, which can complicate hiring, marketing, and (if you sell anything physical) channel delivery.

If we had single-payer health coverage, I think we'd be the best country to do business in.