Fighting a war on another continent can be a difficult experience. Here's a tip for making D-Day a little less tramatic by taking advantage of the AI's inability to wage war.
Once the AI has built railroads, he will respond to your invasion force IMMEDIATELY with almost every mobile unit in his entire arsenal. By fortifying your high defense infantry on a mountain with a railroad connection, you can pretty much wipe out his entire army in one turn. Make sure you are already at war with the AI, so he will attack your units on sight.
1. Split your forces in to 2 groups: Have a large invasion force ready - generally two full transports are necessary to be successful in modern ages. Also have a vanguard landing force - which is just infantry.
