Here's a better, more holistic overview, in case you want to see what starting "from nil" actually entails (hint: you don't just step off a plane and tell Uncle Sam that you want to be a citizen):
https://immigrationroad.com/green-card/immigration-flowchart...
> The time it takes to become a permanent resident varies dramatically, affected by many factors such as USCIS processing, visa availability, labor certification/background check delays, the applicant's qualifications, nationality, residence, profession, luck, and so on. Most people are probably looking at 5 - 15 years. Some also spent several years in a nonimmigrant status prior to starting the immigration process. After green card, add roughly 5 - 7 years towards citizenship
In addition to the time, as others said there's a high probability the path will fail for most. The process starts with winning a visa that allows you to immigrate (tourist/business/student visas don't count). I say "win" because you need to find a company willing to pay and apply for that on your behalf, go through a lottery based on degree to see if you even get the opportunity to apply, and then hope the application isn't rejected on the grounds of the job being something a U.S. citizen can do. if you studied in the U.S., you get 1-2 more years to work under your student visa on what's called "Optional Practical Training" to convince your employer you're worth the hassle of sponsoring an immigration visa. Once you have that visa (e.g., an H-1B visa), you have 3 years to try rise to a senior position and convince your employer that you are valuable enough to splurge on a green card application. If that fails, you can apply for a 3 year extension and try again. If that also fails, you must leave the country for at least a year, and start over. If you succeed, you wait some number of years depending on your birth country and quotas imposed on each before you get the chance to start applying for a green card and get this process rolling. Hence 10-22 years, for those lucky few who didn't get rejected at any of the aforementioned points.