I don't think anybody have got waivers to carry cargo from Gulf ports to platforms in the GoM. There are more than enough cheap US-flag vessels that does that on a daily basis. No foreign flag boat could, or would, try to, compete in that market.
When it comes to CSVs carrying the tools and equipment they need to perform work in international waters, but within the US EEZ in the GoM, they are required to get a waiver from the Jones Act.. (Or, according to c,captain, a waiver from the OCSLA for crewing, since the Jones Act don't apply) (???)
As far as I understand it is common to use Jones Act vessels to carry such tools and equipment to the CSVs working in international water, then do a risky transfer in open waters to bypass this requirement, whichever it may be. Some things, like coiled pipes and other very heavy equipment doesn't lend itself to easy offshore transfer, in which case waivers are given. (Pls. correct me if I'm wrong)
As to your suggestion that the oil companies should built or finance boats able to do the jobs; I think you would be disappointed by their reply. If you think that will work you will be disillusioned.
Oil companies worldwide have gone away from owning rig or boats long ago for the reason that they can charter what they need with less cost and risk then owning and operating. Besides, they want the job performed NOW, not in a couple of years time.
I don't care if they are American based companies or not, they will not pay a penny more to have the honour of having US flag, or US mariners onboard, as long as there are existing vessels and crews that can perform the work safely and efficiently already available.
When American Owners realize that they have to build (or BUY) vessels to meet the requirements they will be able to compete, even in their home market, NOT BEFORE.