it's not transition altitude, it is transition level because in the
U.S. it is FL180. The TA is 17.000 ft
On all the USA Jepp charts I've ever seen it states that
Trans level: FL180 Trans alt: 18000'
with a proviso in the WWText that at certain low values of QNH some FLs won't be available as they will be below the transition altitude.
The USA and Canada adopted the 18000/FL180 transition as it is generally higher than most of the mountainous areas of each country. The notable exceptions being Mt McKinley in Alaska and Mt Logan in the Yukon.
Regards,
BH.