There is no law forbidding U.S. investment in Greenland and Denmark. No need to invade it.
Actually, Greenland and the U.S. have been cooperating for 20 years and U.S. investment is welcomed. It's just that no many investors have shown interest in Greenland so far, apart from mining companies.
https://dk.usembassy.gov/u-s-greenland-joint-committee-statement-october-25-2024/
Same on the military aspect. Greenland is part of NATO and there is already a U.S. base, and as far as I know, Greenland and Denmark have not rejected any offer to create more bases.