Yes, if they are born in the US, they are US citizens.
Yes, US citizens can work in Germany with the appropriate visa and work permit.
US citizens can work in almost any country if they have the proper visas. These countries can include Canada, Great Britain, France, Spain, and many others.
No, US citizens cannot work in the UK without a visa.
Yes, US citizens can work in the UK, but they may need to obtain a visa or work permit depending on the type of work and length of stay.
American Indians, yes.
Puerto Ricans are American citizens, therefore, we do not need any type of visa to work or study in the US.
there are 304,059,724 people in the U.S. who are citizens, but there is probably more because of illegal immigrants.
100
No.
Most American citizens don't even know the state capitals of their own country. Also many of them speak on many dialects (Engrish, Ebonics) so requiring a minimum to function and work in the American society is deemed as a necessity.
Not everyone in a U.S. territory is a U.S. citizen (American Samoans are not), but Guam residents are U.S. citizens.