Irish ancestry lies in the lineage of a very large portion of the population of the United States (with the 2008 American Community Survey estimating it at over one in ten) so needless to say Ireland boasts many individuals in all parts of the country. The Irish culture doesn't necessarily bleed through all those with Irish descent though, as Americanization, the culture of “who cares about culture?”, has swept many once traditional families into its vortex. If you're an Irish lad looking for a good lass or vice versa, there are still plenty to be found in America, as long as you know what you're doing.
There is a long history of religion being a very important aspect of both Ireland's culture and the ethnic identity of those in America with Irish descent. Catholicism is prevalent among the Irish (hence the popular term “Irish catholic” used to describe people who fall into both categories) while protestantism has had a big role in Ireland's history as well; either way commitment to one's faith is something to be respected and admired, and something to be expected when dating an Irish individual. An up front conversation about religion and it's importance or lack of importance in your life should be considered when you begin dating.
The Irish have made a significant mark in the workplace in the United States as police officers and firefighters. This was more prominent several decades ago but it still remains true that (particularly in the northeast and in large cities) many forces are dominated by men of Irish descent. This doesn't mean you should go spray paint a leprechaun on the door of the next cop car you see and wait for some Irish attention, but there's no harm in going to the police department to ask for some of their routine services (fingerprinting, residential stickers for your car, background checks, home inspections etc.) and see who you come across while you're there.
Saint Patrick's Day is a testament to the impact that Ireland and Irish culture has had on the United States. It's interesting to note that the first St. Patrick's Day was celebrated before the Declaration of Independence was even drafted (put together by Irish soldiers in the British army), so this is a long standing tradition that has only grown stronger over the years. At this point St. Patrick's day is recognized and celebrated by countries all over the world but the United States organizes the most epic celebrations (as well as being the primary enforcer of the “wear green or get pinched” rule). If you have the ability to, you should definitely attend the huge Saint Patrick's Day parades held in New York, Boston or Savannah, as these are the biggest three held in the United States. Take advantage of the holiday that essentially celebrates you, and get out there.
Irish pubs are scattered throughout the United States (kind of an advantage that comes along with the stereotype that the Irish love to drink). Chances are that there's an Irish bar somewhere in the vicinity of where you live and chances are that you'll like the cultural atmosphere of the venue even if you don't walk in and see your soulmate downing Guinness. If you've got an accent or an “O” at the beginning of your surname then you're automatically a popular customer from the second you arrive (as opposed to the American wannabes). Pubs can be a great place to go to take a load off and have some fun and the relaxed mood is perfect for meeting other Irish singles with minimal effort.
The Irish tend to be a bit more traditional while dating in terms of being with just one person at a time (where in America it is somewhat accepted for men and women to date multiple people until they choose to be exclusive with one of them), so if you've fallen into the American mindset of being single and “playing the field” until you find the right one, take a step back from that when dating Irish men and women, or you may end up offending your dates or hurting their feelings (this type of thing is dependent on how culturally traditional your date is, of course, but as a rule of thumb it stands).
The Irish American Cultural Institute provides programs that run nationwide and bring many Irish Americans together to celebrate culture and tradition. While it's not exactly intended as a matchmaking service, I'm sure no one would mind you using it as such. With events like the Irish Perception Series (a lecture circuit of sorts with performances designed to bring the Irish culture to towns across the country) and The Irish Way (a study abroad program for teens; great way to meet Irish parents) the Institute offers a multitude of opportunities for networking with other Irish Americans. There are other cultural organizations in America devoted to the Irish (the Irish American Heritage Center, the Irish Cultural Centre, and the Irish American Heritage Museum are certainly all worth checking out), but the Cultural Institute is leading the way in terms of making its mark throughout the United States. Find out when the events are and attend; the cultural pride you will be displaying by being at such an event will be an automatic attractive quality to everyone there.
The Irish are a huge part of what the United States is today as well as major contributors to its beginnings. Cherishing and adhering to your culture and traditions while existing in a society with a different set of values can be difficult, but it is quite admirable and something worth striving for. There's no one better to share your Irish lifestyle with than one who shares your roots, and all you have to do to make that happen is be at the right place and be Irish.