If it is, as you say, a US Airways to Lufthansa connection on the same ticket, you have nothing to worry about.

Arriving from the US, you will have to pass through immigration and a security check (customs will be at TXL), but MUC's Terminal 2 (which Lufthansa and its partners use) is specially set up for short connections, so that this is enough time for everything under normal circumstances. It usually works a treat.

If your US flight is delayed and you miss your connection because of it, LH will automatically rebook you to one of the many later flights to Berlin.