Eire and Egypt has no strategically significant advantage over any other nation. They have tactical advantages at the moment, due to their successful expansion as nations. Eire being isolated on an island brings forth many vulnerabilities. If they lose naval superiority, they can be occupied for cheap warscore in Norway, Bretagne, and even Ireland proper. Currently England is the only consolidated mass of land where they can not be easily and quickly overrun.
In this game, all nations are designed to become possible all-around superpowers. That means navally, on land, tradewise and otherwise economically. We are trying to go away from the notions of "Austria is a landpower" and "England is a naval power". If you do not work on, say, a navy, of course other nations will try to use that disadvantage. Hopefully, you'll have made up for this lack of power by becoming stronger in some other field.
I can guarantee that when colonization start, many nations will already have agreed on some area of the New World where they want to establish themselves. For some, it will become a race, for some it will be quite unrivaled. And some will not bother. There is no pre-defined notion that Brazil is Portugal's, or that North America is English. If you want to go to North America, go ahead. Do your worst. And use your current power to manipulate, diplomatically as well as militarily, the opposition away from your target area. Is Eire the strongest now? Be creative and strike a deal with them! Is your nation weak and in need of aid? Contact another nation and propose to share an area of land with them! There is always something to offer.
I agree it's not 100% balanced, but it's a good approximation. As soon as we started playing, we all started disbalancing things to try to get on top. Frankly, I am just happy that Neustria actually felt their sucky monarch. It just shows that the monarchs do count. When you get your 8/8/8 and 9/9/9, the story will be so much different. Conversions, morale, stability, badboy, ... so many factors will become positive modifiers.