Switzerland: your effective rate depends on the canton, and so does your US credit.

Because the credit is limited to tax actually paid, the canton you live in changes your US result. A move from a high-tax to a low-tax canton can create a US liability where there was none, which makes an internal Swiss move worth a conversation before the lease is signed.

Pillar 2 and pillar 3a defer Swiss tax. Whether they defer US tax depends on how each arrangement is characterised, and the answer is not uniform across employers. Contributions, employer matches and growth inside the plan each need a position.

Cantonal wealth tax is levied on net assets, not income, so it is generally not creditable against US income tax — a real cost rather than a timing difference.

Swiss banks report US account holders under FATCA, and the FBAR threshold is easy to cross here without noticing: $10,000 across all foreign accounts at any point in the year. A pillar 3a account and an ordinary current account can reach it between them without either looking substantial.

The federal layer of Swiss income tax is modest; the cantonal and communal layers carry the variation. That is why the canton rather than the country decides how much creditable tax there is, and why an internal move is a US tax event as well as a domestic one.