“If any provision of this Act [amending sections 405, 408, 416, 421 to 423, 1382c, 1382d, 1382h, and 1383 to 1383span of this title, enacting provisions set out as notes under sections 405, 421 to 423, 907, and 1305 of this title, and amending provisions set out as a note under section 1382h of this title], or the application thereof to any person or circumstance, is held invalid, the remainder of this Act and the application of such provision to other persons or circumstances shall not be affected thereby.”