@hightor,
hightor wrote:I don't know that there are any countries where you can just cross a border, legally or illegally, and declare yourself a legal resident or citizen.
In Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, and Switzerland you can do so ... well, sometimes nowadays at some borders, since many countries have established temporary border checks.