One should not confuse ISM bands with license-exempt services. Even though some of them share allocated frequencies, they are not synonymous! The regulations for one service cannot simply be applied to the other.
Example: 44 meters has an international ISM allocation that's implemented in both the US and Canada. License-exempt communication/non-specific-use devices are also permitted on those frequencies in Canada under RSS-210 rules, but not under FCC Part 15 in the US.
Other ISM bands in the US are shared with specific other radio services, like 11 meters (CB radio) and 33 cm (Amateur Radio), and also license-exempt devices. But over half our ISM bands are simply not available under Part 15, except under tightly limited circumstances, if even then.
Conversely, some of the most popular bands for license-exempt devices are not ISM bands at all: 160-190 kHz, 510-1705 kHz, 49.86 MHz, and the FM broadcast band.