One of the biggest US health insurer is UnitedHealth Group. In their last financial quarter report they published:
Revenues $48.7 billion
Earnings From Operations $3.4 billion
Net Margin 4.5%
These type of good and enviable stable profits are not enough to explain the inefficiencies in the US. Insurance may be lobbying but that is dwarfed e.g. by the marketing expenditure of the pharmaceutical industry (same level as their R&D). Yes health insurance is living well on the inefficiencies and their (in part unnecessary) middle man role but there are way bigger money leaks.