Technically -- the 'united States of America' ( lower case 'u' ) is a group of 50 separate "countries" - each 'state' being a
sovereign country unto itself ( i.e. - like Israel is a 'state' ) - bound together in agreement for a common purpose and cause ( freedom ).
However, the 'United States of America' ( upper case 'U' ( or in ALL-CAPS ) ) is a 'corporate' entity ( essentially, the Federal Government - but, technically, in an 'abstract' existance ( the "non-existant" one that I am pretty sure the OP is referring to ) ) which, constitutionally, was ever only intended to perform about 5 functions (
and, strictly for the sake of - and service to - the 50 sovereign states ) -
no authority is given it for anything else - and, in fact, is expressly
forbidden.
Any U.S. citizen's name - written in ALL-CAPS on a government document - does
not refer to an actual real person - but, rather - to a "non-existant" 'abstract' "person" with whom the government has made an association for the purpose of "business dealings"...
There are many more of these interesting facts - if you know where to look...
There is a "booklet" that every U.S. citizen should read -- it is called
The Citizen's Handbook. Find you a copy and read it. If the booklet is not about
Jury Duty, you have not found it yet...