The answer is in the article.

Ah, must have accidentally skipped of that part. Cheers!

For anyone else: “ While STTARS has previously transported Webb components to other NASA or partner facilities primarily by air, the team chose to transport Webb by sea to Kourou due to the logistics of landing at the Cayenne Airport in French Guiana. The 40-mile (65-kilometer) route between the airport and the launch site features seven bridges that STTARS would have been too heavy to cross. In addition, the drive from the Port de Pariacabo to Webb’s launch site is relatively short. In comparison, a drive from the Cayenne Airport to the launch site, factoring in STTARS’ slow speeds and other constraints, would have taken about two days.”

Also the package is about 1 foot too tall to fit in an AN-225.

Telescope in feet 110x18x15

Antonio AN-225 cargo 142x21x14

Edit: it would fit in a Beluga 124x23x23

It also fits in a C-5

Next question: Why does it need to be launched from another continent? Why not FL or TX?

Because they're launching on an Ariane rocket, which is a French rocket that launches from French Guiana.

As to why they chose that, I have no idea

> The rocket had a streak of 82 consecutive successful launches between 9 April 2003 and 12 December 2017.

That's why.

(We also like international cooperation. We build the telescope, ESA chips in with the launcher. Same situation with Orion and the ESA's service module.)

You get an advantage launching closer to the equator. The velocity of the Earth at the equator is higher so less deltaV is required from the rocket itself when compared to launching somewhere closer to the poles.

You get a speed boost the closer you are to the equator and if you want an equatorial orbit you have to spend fuel in orbit to correct down to zero degrees.

It is way cheaper to correct these things on the planet than with bigger rockets.