SCHIP Expansion Act of 2004 - Amends title XXI (State Children's Health Insurance Program) (SCHIP) of the Social Security Act (SSA) to: (1) make all uninsured children eligible for SCHIP; (2) prohibit the State from excluding a child who has access to high cost coverage under a group health plan or health insurance coverage from being treated as a targeted vulnerable child under SCHIP; (3) increase Federal financial participation under SCHIP and Medicaid for States with simplified enrollment and renewal procedures for children, regardless of their family income; (4) provide for an increase in funds under SCHIP and Medicaid for outreach strategies for children; (5) increase funding for SCHIP; (6) prohibit payments to a State with an enrollment cap (or related procedures) which has not exhausted its available allotments; and (7) provide for the application of Medicaid managed care requirements to States under SCHIP.