I got to the impression that because of differences for the used similar sounding abbreviations - e.g. MSA - on the two sides of the pond, a bit of a confusions has started and there is talking about two different items. Here in good old Europe itīs all ICAO !!
To solve that, read this:
SKYbrary - Minimum Sector Altitude
aterpster, the difference in shown heights of the mountains could also come from a different charting base. Normally it all should be WGS 84, but could it be possible that some people still use other geo ref systems or simply stick to old procedures ?