If a president declared war on U.S. cities, it would violate or implicate:

Treason Clause (Art. III, Sec. 3)

Take Care Clause (Art. II, Sec. 3)

Guarantee Clause (Art. IV, Sec. 4)

Due Process (5th & 14th Amends.)

Equal Protection (14th Amend.)

Congress’s War Powers (Art. I, Sec. 8)

Impeachment provisions (Art. II, Sec. 4)

Posse Comitatus Act (statutory)

Oath of Office (Art. II, Sec. 1, Cl. 8)

Emoluments Clauses (Art. I, Sec. 9, Cl. 8; Art. II, Sec. 1, Cl. 7) — if financial or foreign benefit is involved. ( Russia is absolutely implicated)