Most working ranches, cattle drives, pack trips, covered wagon rides and guest ranches in the USA will be able to accommodate riders up to 250 lbs, but this is not the case for most inn to inn riding tours, faster paced wilderness rides or horse drives.
In Canada all rides are fine except the Charlevoix and Gaspe Peninsula rides in Quebec.
All rides in Ireland and England will be OK as well, since they are using very sturdy Irish Sporthorses or Welsh Cobbs.
Also all rides in Iceland and Norway are OK to book up to 250 lbs due to the unique body structure of the Icelandic horses.
All rides in Germany and most  in Austria are fine.

The following countries in general use a smaller or more fragile horse breed and will (as a general rule) not accept any riders over 210 lbs - exceptions are listed on the left side:
Europe
Bulgaria  France   Greece   Hungary  Italy  Portugal
Scotland  Slovenia  Spain  Wales
Central and South America
... all countries with few exceptions
Africa
... all countries with few exceptions
Oceania
Australia  New Zealand
Asia
... all countries

Some of our trips have one or two horses available that can carry a heavier rider, but they may not always be available.

Selle Francais

Welsh Cob

Clydesdale

Icelandic

Akhal Teke