What six states have two or three football teams?

In the NFL : New York, Ohio, Texas, Florida, California and Pennsylvania.

Source : http://www.nfl.com/teams/

Missouri also has two football teams, the Rams and the Chiefs.

Maryland has 2 NFL teams playing in the state. The Baltimore Ravens and Washington Redskins.

In 2020, seven states have 2+ teams:

California (3): Los Angeles Rams, Los Angeles Chargers, San Francisco 49ers
New York (3): Buffalo Bills, New York Giants, New York Jets
Florida (3): Jacksonville Jaguars, Miami Dolphins ,Tampa Bay Buccaneers
Texas (2): Dallas Cowboys, Houston Texans
Pennsylvania (2): Philadelphia Eagles, Pittsburgh Steelers
Ohio (2): Cincinnati Bengals, Cleveland Browns
Maryland (2): Baltimore Ravens, Washington Football Team

https://worldpopulationreview.com/state-rankings/nfl-teams-by-state

As of the end of 2020, a total of seven US states have more than one NFL team:
California - Los Angeles Rams, Los Angeles Chargers, San Francisco 49ers
Texas - Dallas Cowboys, Houston Texans
Florida - Miami Dolphins, Tampa Bay Buccaneers, Jacksonville Jaguars
Ohio - Cleveland Browns, Cincinnati Bengals
Pennsylvania - Pittsburgh Steelers, Philadelphia Eagles
New Jersey - New York Giants, New York Jets
Maryland - Baltimore Ravens, Washington Football

However, as there is, as we know, more than one code of football, we can also say that four states have more than one MLS team:
Ohio - FC Cincinnati, Columbus Crew
Texas - FC Dallas, Houston Dynamo, Austin FC
Florida - Orlando City, Inter Miami
California - Los Angeles Galaxy, Los Angeles FC, San Jose Earthquakes

Although the New York Metropolitan Area has two teams, New York City FC are based within the city limits, while the New York Red Bulls are based in Harrison, New Jersey.

In Australia, the eighteen teams of the Australian Football League are split between the five states of the mainland, with two each in Western Australia, South Australia, New South Wales and Queensland, and the remainder in the game's major stronghold of Victoria.