Though abbreviations for such words as chapter (ch.), edition (ed.), page (p.), or pages (pp.) are common in source citations, they are not appropriate in the body of a formal academic text.

Place-names and months of the year are often abbreviated in source citations, but they should almost always be written out within sentences.

Common exceptions are Washington, DC, and U.S. US is usually acceptable as an adjective, and it may be written with or without periods. However, check your style guide or your instructor's preference before using US (or U.S.) as a noun.

The U.S. delegation negotiated the treaty.