The US issues a visa bulletin every month (this month's bulletin) that gives information regarding whose priority date has become current and who shall wait approximately how much.
You can see that India, Mexico, China, Philippines have oversubscribed the annual limit, so there is a huge backlog. But what about all of the rest of the countries in the world? Say Russia? Or UK? Or Portugal? Or Australia? What about them? Are green cards immediately available for them?
You can also find a column named "All Chargeability Areas Except Those Listed". What's this? Does this include European countries, for example?