I thought it was 2.5% for German cars in the US? Is it 4% now?
Also, what's your source for the 90% VAT on US cars sold in Germany? A search didn't find a reference, and VAT in Germany ranges from 7% to 19%. There's a 19% import VAT that is waived if certain residency conditions are met (i.e. you're intending to live in Germany as a resident), and is
equal to the regular VAT that people pay for goods bought within Germany, including German cars manufactured in Germany. Basically,
from what I'm reading from the German government website, it appears to be
similar to how sales tax laws work here when bringing goods from one state to another and is intended to avoid sales tax shenanigans: if you buy within Germany, German VAT at 19%; if you buy non-EU 19% VAT; if you buy non-EU and intend to establish residency, fee (maybe) waived; if you buy non-German EU, fee reimbursed to the extent that you paid VAT in the other EU country (i.e. if you paid 15%, then you get a credit for that amount).
I can see how military contractors can get screwed by this (military has VAT waiver/reimbursement), or other temporary residents bringing a car in, but is it really a tariff issue? And even if it is (it's not), 19% is a faaaaar cray from 90%. So I guess I'm just asking for a source aside from your own expertise.