Born and raised in Scotland (Aberdeen and surrounding area), now living in London.
Soccer: Aberdeen, Scotland, whoever’s playing against England.
NFL: Bills
Er, that’s it. I’m used to my teams losing.
No.
Philadelphia has a deep history of producing world-class boxers.
Grew up mostly around Washington DC, so my teams are the Redskins and the Capitals. MLB only came back a few years ago, and sadly, of course, Washington has had no pro basketball since the late '70s.
Born and raised in west central Scotland, now back there after time spent in London (and Kent) and Harrisburg, PA.
League Soccer: (Glasgow) Celtic, Hamilton Accies, Charlton Athletic
Intl Soccer: Scotland, USA
Intl Cricket: England
MLB: Phillies
Never could get into NFL, and while I enjoyed watching hockey I can’t say I supported any particular team.
From upstate New York, lived in southern Virginia for most of my life.
MLB: Mets
NFL: Chargers
NHL: Ducks
NBA: Basketball can ram it
NCAA everything except basketball: Virginia Tech Hokies
NCAA basketball: can ram it
The only teams I’m really committed to are the Mets and Chargers. If there were a professional Virginia team for anything else (D.C.-lite VA doesn’t count), I’d probably throw my hat in with them. Except for basketball, which can ram it.
Packers
Twins
Sheffield Wednesday
Loved the Blue Horizon when I lived there. But I think he was commenting on your use of “route” instead of “root.” 
NY Giants
NY Knicks
Lakewood Blue Claws (no love for MLB, but the Blue Claws stadium is five minutes from home, and there’s nothing like a summer evening at the ballpark).
NFL: Denver Broncos. It has been a sad year.
MLS: FC Dallas
International Soccer: USMNT
EPL: I’m new to watching it but I kinda like Liverpool so far.
My teams are the NY Mets (season ticket holder, in fact) and the NY Knicks (a mostly dormant love slowly getting rekindled). I casually follow the NFL with a preference for the local (not quite NY) teams, the Giants and Jets. I couldn’t name more than 2 players on either team but I tend to root harder for the Jets as traditional underdogs, yet have a big Giants fan as an in-law so I probably watch more Giants games than Jets games.
Never got into NHL, MLS or any other pro sport. Will watch Grand Slam tennis. Don’t see the point in actually following NCAA sports as a sports fan.
I take it you don’t care much for basketball? 
In order:
New York Giants
New York Jets
New York Rangers
New York Knicks
New York Mets
New York Yankees
I don’t actually like basketball or baseball, but I’ll check in on late-series playoff games if New York teams are involved. The only New York team I actively dislike is the Islanders.
World Soccer: US
MLB: NY Mets
NFL: Giants
EPL: Aston Villa
NCAA: Rutgers, Big East (minus TCU), UT
NHL: NJ Devils
NBA: Knicks/Nets
A man (or woman) of taste, discernment, and complete and total masochism, apparently.
I grew up in central Illinois.
MLB: Cubs
NFL: Bears
NBA: Lakers
Non-hockey fan
NCAA: Florida Gators (with the Southern Illinois Salukis as my 2nd favorite)
Born and raised in Baltimore, although I’ve been living in L.A. for going on 18 years now.
NHL: Capitals
MLB: Orioles
NFL: Ravens
College: Maryland Terps. I didn’t go to U of M, but both my brothers did, and my whole family are pretty much Terp fanatics, and my own college was not exactly known for its sports program, so they’re my team by default.
Canadian living in Portland, OR.
Sports I truly get hyped about, in order of interest:
NHL - Vancouver Canucks
WHL - Portland Winterhawks - local team eh.
CFL - Saskatchewan Roughriders
NFL - Seattle Seahawks - localish team. (Back when I lived in Canada I had been a Raiders fan)
Sports I’m somewhat interested in:
NBA - Trail Blazers - (I never had a favorite NBA team prior to moving south)
NCAA - Oregon St. (family ties)
Born and raised in St. Louis.
Cardinals - MLB
49ers - NFL
Missouri (alma mater ) in NCAA sports
New Castle - EPL
I don’t really follow hockey, or the NBA.
NFL-St Louis Rams
MLB- Cincinnati Reds
NHL- Detroit Red Wings
NBA- Detroit Pistons
NCAA- Michigan Wolverines
npower Championship (2nd tier of English soccer) - Reading FC