If you've looked at the transaction fees lately, you can definitely pay to power an American house for 1 month too (that is, assuming unreasonably that the house was powered at the same cost that most bitcoin miners pay for power: ~$0.04/kWh)

What is that in money, 50 bucks? (Live in Germany, we have very high energy prices, so I relly don't know. Single in 50sqm Appartment, paying 47euros per month for a 100% renewable plan.)

Depends where in the US -- In Texas (as long as there aren't any blizzard-driven blackouts with accompanying rate spikes), retail electricity costs something like $0.10/kWh. In California, it's closer to $0.20/kWh.

So roughly somewhere between $70-$150.

To put it in perspective, ~$1,000,000,000,000 USD is being secured by a decentralized system by using that much electricity. How much electricity/oil/other power is used by the US military to ensure the US government stays in power and the US currency retains its value? Surely orders of magnitude more energy than what is used for Bitcoin.

The number of transactions that are completed on the base layer is not the relevant metric. As the technology matures and as Bitcoin is more fully monetized, transactions will happen on higher layers. The "high" energy cost is necessary to secure the decentralized system.