But the geography of Liberty works against itself. It's like a funnel. Texas is the only way into New York, and Rheinland would have two entry points open to them to get in. Reinforcements would have to arrive from New York one at a time. Feasibly, if Rheinland were to blitzkrieg capture Texas, Liberty wouldn't be able to re-take it since only one ship could jump through at a time, which would get obliterated by the garrison.
The SP mission where you enter Rheinland comes to mind, with the dozens of capital ships positioned at every Jump Gate.
Edit: Adversely, Rhienland's geography is much looser. There's a lot of places to attack fleets from a flank. But the Hessians are pretty much all around them.