How many law enforcement officers (Federal, Municipal, state, etc. )
are there in US?

An fairly recent estimate is the best you can hope for as an answer.
Homeland Security does not disclose how many sworn officers it has and
neither do other many other Federal entities.

tutuzdad-ga

Here's your fairly recent estimate... APPROXIMATELY 375,000 people are
currently working with law enforcement agencies in the United States.
The breakdown is below:

There are 3500 Sheriffs Offices in the United States with an average
of 24.5 Officers per office (approximately 85,750 sworn in).

Approximately 83,500 in Federal Offices: CIA - 22,500, FBI - 17,000,
Border Patrol - 11,000, Federal Protective Services - 12,000, Secret
Service - 5,000 (2,100 Special Agents, 1,200 Uniformed Division, 1,700
Technical Division), DEA - 16,000 (11,000 Unformed Agents + 5,000
Special Agents).

Police Departments account for just over 205,000 officers. Here are a
few of the major cities for ya:

NYPD - 40,000
SFPD - 2,000
LAPD - 9,000 + 525 with LA School PD
Washington DCPD - 4,000
Chicago - 15,000
Boston - 1,500
Philidelphia - 6,600
Seattle - 1,500

Hope this helps! Good luck to you!

       - EP -

You left out:

Bailiffs
Constables
Justices of the Peace
Prosecuting Attorneys
Coroners
Military Police (over 50,000 of these alone)
Special Police
Railroad Police
Park Rangers
Game Wardens
Prison Guards
Coast Guard (who also happened to be commission law enforcement officers)
Forest Service
USDA Inspectors
Truant Officers
Fire Marshals
Town Marshals
Reserve Police
Postal Inspectors
National Marine Fisheries Service (NOAA Law Enforcement)

...just to name a few