What is the point of the TC container?
1. It is cross-platfrorm
2. It hides the
fact that you have armory (bitcoin) wallet
3. It works in Tails as persistent container
Also, as Wachtwoord suggested, why bother with two USB keys? Can't you just get yourself a single, large USB key, and partition it into OS (Tails) and data (Armory + wallet files)?
Yes we can

Tails is Live-CD/Live-USB distro. That means no data is saved after shutting it down, moreover Tails mount ALL disks as read-only. But data can be saved on encrypted partitions, it is achieved with Truecrypt containers OR special "Tails Persistent Volume" with Luks encyption. With first one you have to boot Tail by whatever method you choose - DVD, USB-drive, Virtualbox, etc. and have TC-container on whatever disk (even on that you booted from). The last one you can get when you install Tails on USB stick with built-in "Tails LiveUSB installer": so you will have two partitions on one USB - one for Tails installation and one encrypted persistent volume you mount when you boot from USB. You should really spent some time and try Tails
