Trade sanctions due the USA trying to annex Greenland would tank the stock market so hard and stay crippled for many decades to come.
USA won't annex Greenland.
Greenland belongs to Denmark. Denmark is part of the EU. EU has a nominal GDP of 19 trillion which is more than China's 18 trillion. (USA is 29 trillion).
USA has already a bad standing with China due to the Taiwan situation. You don't throw away exports to economies with 37 trillion combined nominal GDP.
Denmark is part of the NATO. NATO nations buy weapons from other NATO nations. USA is the biggest weapons dealer in the world. There's a giant industry in the US relying on weapon exports to other NATO countries.
What's even more important: One of USA's biggest military base outside the states is in the EU (Ramstein, Germany). Ramstein serves as a headquarter for all US military operations in Eurasia and Africa.
Annexing Greenland would be a net lose of unbelievable proportions for the USA.