An American cover letter is a sales document with strict manners. It sits next to the resume — the word 'CV' is reserved for academic and medical applications — and its job is narrow: explain why the results already on that resume matter to this employer. Recruiters in the United States read it in well under a minute, so the first two sentences decide whether the rest is read at all.
The format is settled enough that deviating from it reads as carelessness rather than personality. US Letter paper, one side, 1-inch margins, a month-first date ('September 16, 2026'), the recipient's name where you can find it, three or four paragraphs, and a formal sign-off. Nothing about your age, nationality, marital status, religion or health appears anywhere in the application: US anti-discrimination practice keeps those out of the hiring process entirely, and a photo on the resume is unusual outside modelling and acting.
Salary is the other American particularity. A growing number of states and cities require employers to publish a range, and several forbid them from asking what you earned previously. Unless the posting asks for your expectations, leave money out of the letter; it is negotiated later, from a stronger position, once they have decided they want you.