France is also a US ally. I would rather suspect the answer is that the French company is more willing to bend over to censorship and surveillance orders from the Greenland government.
Sure, but Starlink, 5eyes, Palantir and some drunk misfit defsec would never...
France is an ally of the US, but not of the current government.
The US diverts trunks for interception and active attacks all the time. Jamming the internet to Greenland during an invasion would be trivial on multiple levels. This will make virtually no difference to national security. Good for the monopoly provider though.
If the concern is jamming, the solution is to have a diversity of service providers, not to assume you know who your enemy will be in a decade from now.