After taking the survey at http://agglaw.polldaddy.com/s/irelandnisurvey and subscribing to this blog (see left column)…
Register the IP you’ll use in the US, most likely your trademarks. Many Irish and Northern Irish companies mistakenly believe that their home jurisdiction trademark registrations will be effective in the US. Nope. Also, some will think that the Madrid Protocol causes their home jurisdiction approvals to be effective in the US. Nope. The Madrid Protocol is useful in determining applicant priority, but doesn’t operate to extend a home jurisdiction registration.
I always encourage Irish and Northern Irish companies to inventory their IP that they intend to use in the US before they expand to the US. Part of that effort is to ensure that we’ve properly protected what needs to be protected, and part of it is to ensure that, to the extent needed, any intercompany agreements have the proper scope.
Logos, trade names, product names, etc., can be trademarked here. The US is not a first-to-file trademark registration jurisdiction (where the first to file may prevail even if they are not the first to use–China is, for example, a first-to-file jurisdiction). And, yes, the US does allow for common law trademarks that arise from usage. But the most effective way to protect the value of those marks–the value built in Ireland and Northern Ireland and leveraged in the US–is to register. A basic trademark registration can cost less than $2,500 (with no opposition or other weird developments), and that’s a small price to pay.
The reason I suggest that this is the second thing to do is timing–the USPTO takes a little while to review applications, and may have questions. This isn’t to suggest that you wait on US expansion until after you obtain appropriate registration–you shouldn’t–but you should have your registrations in motion (submitted) when you hit the US market.