There was a time when a person from any country could become a US citizen by serving in the US Military. I don't know if this is still true or not. Check the web sites for the Army, Navy, and Air Force and/or call one of the recruitment offices which I am sure are listed on their web sites.
Quick answer, no. The Armed Forces of the United Kingdom accepts only UK citizens and citizens of Commonwealth nations, with exceptions granted to citizens of the Republic of Ireland and members of the Brigade of Ghurkas of the Royal Army. If you're a US citizen with Dual Citizenship in a Commonwealth country (i.e., South Africa, Canada, Australia, New Zealand, Bahamas, Cyprus, Zimbabwe - if your date of birth was prior to their withdrawal from the Commonwealth - Dominica, etc.), it may be possible. As a sole US citizen, it is highly unlikely, if not outright impossible. See related link "Entry Requirements: Careers: Royal Marines Home"
Please note however:
Numerous members of the USMC have served, and still do, on attachment with the Royal Marines (RM & USMC have a "Bond of Friendship"). Indeed, it's commonplace for the two marine corps to have exchange personnel in their respective training establishments (eg recently the chief PT instructor for the USMC's OCS at Quantico was a RM "Colour Sergeant"), and they frequently engage in joint training, especially in FAST, and general amphibious operations.
The links are particularly close in areas like sniping (each regularly send students & instructors to each other's sniper schools), Advanced Warfighting & Amphib Ops (many RM officers attend these "laboratories"/ schools, plus general staff courses, & other courses at the USMC University), Mountain & Arctic Warfare (some US Marines do the British Mountain Leader course - much longer & more varied than their own courses in this area), and Reconnaissance/ special ops - there are always USMC Force Recon/ MARSOF types at the RM's SBS base in Dorset, and presumably the converse is also the case.
Any USMC posted to serve on attachment with RM have to pass the "All Arms Commando Course" (a prerequisite for all personnel who want to be in 3 Commando Bde, RM: all attached British personnel - eg Army gunners, engineers; RAF FACs; Navy medics etc, have to pass it too), and it's rare for them to fail - because they're well briefed about what to expect, & chosen because they're the types likely to adapt readily to the RM way of doing things.
As indicated above, to join the Royal Marines you have to be a UK or Irish citizen, or citizen of a commonwealth country who is resident in the UK. There are, however, Royal Marines who have US as well as British citizenship (often sons of Royal Marines born in the US when their fathers were serving on exchange with the US Marines!), and some US Marines serve with the Royal Marines on exchange, usually as platoon commanders or sergeants, and sometimes company commanders.
Yes. When I enlisted, I was required to have first established permanent residence in the US, and to have declared an intent to obtain US citizenship. I don't know if those stipulations are currently in effect still.
Any recruiter for the specific branch of service you wish to join would suffice. You can go to the US Army/Navy/Marine Corps/Air Force recruiting websites, and even send in an inquiry by e-mail. I enlisted as a foreign citizen in 1997, and at that time, foreign nationals were required to have established permanent residence in the US and to have declared an intent to obtain US citizenship. I can't say with any certainty whether or not that has changed since then.
Yes You Just Need To Move To The USA And Sign Up Its That Simple
Yes but you have to have your balls chopped off with a swiss army knife
A Jamaican can join the US Army if they have a green card or they are a naturalized citizen.
A British citizen can join the US Army, and a British soldier might be attached temporarily to a US unit, or sent to a US training/instructional programme, but they won't be able to be in both services simultaneously.
no
Yes, you do need to be a US citizen
can a no legal status join the US army???
Yes.
nope you have to have a green card first or us citizen
Not even every US citizen living outside the US has to join the US army. Certainly people from other American countries do not have to.
Only a US citizen can enroll in the US military,you will need to become a citizen.
You have to be a US citizen to join the US marines i think its actually permanent resident
Define Work what kind of work? US citizen can not serve British army but can do work in commercially
No matter what country of origin, a non-citizen/ non-resident cannot join the US military without first gaining citizenship.Currently only US citizens are allowed to join the US Army. If a Jamaican has a green card, they may join the Army if they meet requirements.