The United States Merchant Marine, alone, officially has some 400+ ships (minimum 1,000 gross register tons (GRT) tons or more) and if my memories of those early lectures in the USCG hold up, there's another seven- or eight-hundred ships owned by American interests but flagged in other countries. Roughly half work the Pacific, slightly less than half the Atlantic, and the remainder are scattered about the rest of the globe.
Most other "first world" nations have about 100 to 200 ships of similar size in their merchant navies. People without much time around ports are often surprised by the numbers of "third world" nations with sizable merchant fleets, often this is because its an American or a British vessel with a foreign flag, but sometimes its more straightforward. Pakistan, for example, has 12 ships owned by their nationalized shipping company. Tiny and economically poor Greece, believe it or not, has the maritime fleet in the world, over 3,000 ships!
Putting that into Traveller numbers... Well, I'm new to the game, but they should be fairly mundane sights.