A US Citizen would need a work permit to live and work permanently in the UK.
yes
If you're not an EU citizen you will need a work permit.
First off, you're not an 'English' citizen, you are a British citizen. England is not an independent country.
Yes, a United States citizen can join the German Army. Once you have joined the service you can work your way up to becoming an officer.
She would need a UK work visa.
First of all, when British citizen and an American marry's, they become an AmeriBrit and have equal rights to work in both countries on their choosing.
NOPE
Just a work visa
The United States of America, or Australia
No, the Canadian has to be married to the American in order to live or work in America. Because you have to be married to an American to get a green card in order to do that.
England is part of the United Kingdom which is part of the European Union with unrestricted access to work in each others countries. So Portuguese people can work and live in the UK and UK people can work and live in Portugal.