listed 5 factors important for individuals looking to apply for Jobs in the US (as I did coming from Ireland).
Sacha notes the key to a successful application is the ability to market yourself:
 Your CV Must Be "American-ized". American companies expect your Curriculum Vitae to be re-written as a standard "US-style" resume. Any other format will be confusing to the employer and could result in your resume being discarded. American resumes should detail your education, employment history and achievements as in your CV, but in "American English" spelling and grammar. Job seekers should not forget to use the correct American terminologies for their profession as well. Using a distinctly American spell-check program and researching similar US technical terms online will help keep your document understandable. If your CV isn't American-ized, you might as well not even bother applying; the American employer will find a standard CV confusing and may not take the time to read it.
 Be Proud Of Your Accomplishments. In a competitive job market, American employers need a really good reason to hire you over a similarly-qualified applicant. You may not be used to boasting about your accomplishments, but in America your prior successes really count. Think about the last time you successfully completed a project or helped create a "happy-customer" transaction. Make a list of at least three success stories, and be prepared to tell the American employer about them. Employers in the USA love to see statistics, too. List specific statistics related to your work accomplishments in your resume. This will really boost your resume's credibility.
 Keep Your Resume Concise And To The Point. There is an old American saying: time is money. This is no truer than when an employer is looking at your resume. An "American Resume" should be no more than two pages long and be easy to read. Above all, do not state the same information twice. If you have performed the same job for a number of employers or if you have tended to work in the same industry job after job, try to rephrase the job descriptions or find new terms to describe your tasks. This keeps the reader interested, and the resume interesting!
 Attach A Cover Letter And Make It Great. Cover Letters are a one page "soft" or friendly introduction to your resume in the USA, and the same principles of brevity in a resume must also be applied in a cover letter. American cover letters are not personal letters of introduction, but instead highlight your professional skills and outline how you can contribute to the success of the organization you are applying to. And it isn't just about being brief; you must be persuasive and to the point in your introduction. A cover letter is a sales tool. for you. Don't be boring! Employers want dynamic employees, so don't give them a reason not to interview you. You need to write your cover letter with the goal of enticing the reader the employer - to find out more about you. A good cover letter will automatically give you a better chance of having your resume read and considered.
 (Most importantly - my edit) Be Yourself. American employers are looking for a person who will be a good fit for the job. When you are applying for a job to the USA and are many miles away, it may be tempting to overstate your skill or expertise level just to tip reader's interest in your favor. A good resume always clearly states your credentials and expertise for the position but stays on the safe side of hyperbole. Employers may be able to find 100 job candidates who are suitable for the job but they are also looking for a 'real' person who can deliver the skills and talent that their resume promises.
As a sidenote, posting your resume online (using the links available on this site) is a good way to keep track of your progess. A number of these sites provide monitoring data so you can check how often your resume is accessed by potential employers. The more tuned it is to the employer's needs - the greater the number of hits it will receive.