What are the differences of U.S., the U.S., and USA

[Hieupt]

Hi guys,

Please tell me the differences of "U.S", "the U.S", and "USA" in term of usage and meaning.

Thanks,
Hieu.
_________________
Thank you very much,
Hieu Phan.

P/s: Please just correct if I'm wrong somewhere!

[Erik]

There is always a dot after the S as well as the U.
All are very close in usage. The meaning is the same. All are less than the most formal of usages. You sometimes see just US as part of a longer acronym such as USPS (United States Post Office) or USDA (United States Department of Agriculture). The "THE" is used in any place that "THE" would be used if the whole thing were spelled out, such as "The United States". It is a bit more business-like in most situations. "USA" is perhaps a bit more casual, and it is also used for patriotic and supportive situations. If there were a chant at a World Cup football match, they would say U-S-A!, U-S-A! and there is a famous song "God Bless the USA" you would not say U.S. in a situation like that. Tags on goods always say "Made in the U.S.A." and that is an appeal to patriotism (as well as being the law).
Some people also say "U. S. of A." but that seems a bit old fashioned and rural for most folks.

[Hieupt]

Very loud and clear, Erik! Thank you very much for your response! :-)
_________________
Thank you very much,
Hieu Phan.

P/s: Please just correct if I'm wrong somewhere!