wopger, it might concern you even as a German resident. It depends only on the amount. As Jim said double taxation treaties only avoid that you pay more than the tax which is the higher one of the 2 countries (there are exceptions; sometimes you actually do pay even more than the higher rate). They regulate which country has the right to tax what and to which amount. Their main purpose is to ensure the other country has to recognize this already paid tax --- to as the name says avoid double taxation.

It concerns Germans as the higher inheritance tax rate usually is on the US side. Their 40% rate is reached far before such a high rate applies in Germany to inheritances where you can inherit up to EUR 6,000,000 and still pay only 19% (Erbschaftssteuerklasse 1) respectively 30% (Klasse 2 und 3). Only much higher inheritances than that Germany taxes as high as the US --- and even that only if the heir is a distant or not a relative at all.

Result: If the double tax treaty Germany-USA does not limit the % the USA can charge (I had a quick look and didn't find such a limitation) a inheritance of for example $5,000,000 is taxed with around $2,000,000 in the US and those $2 Million are credited ("Anrechnung") against the FAR smaller inheritance tax you'd have to pay in Germany. Because of this tax credit you have to pay 0 in Germany - but you don't get back what you compared to Germany "overpaid" in form of the far higher US tax bill.

In other words: Regarding estate tax Germany usually is far cheaper than the US --- and that advantage lost if you have US assets.