For years, the US has been demanding that European allies spend more on their military

Now that they are, they are also setting up European cooperation mechanisms, and so now the Pentagon is upset about baby steps toward European military autonomy:

For years, the US has been complaining that EU countries do not spend enough on their own military capabilities.

“Now we’re trying to do that, and it’s not right either,” Jean-Claude Juncker, the European Commission president, told delegates at the Munich Security Conference this weekend.

A high-level annual meeting of US and European politicians, generals and defence experts, the conference was this year dominated by calls from Germany and France for Europe to stand on its own two feet — and US qualms about what that might mean for the transatlantic alliance.

Indeed US misgivings about attempts to forge closer defence ties within the EU could become a significant irritant in relations with the US.

Why would Washington have a problem with this?

For the same reason that they expanded NATO to Russia’s border, because they want to ensure that Europe remains a market for US military hardware, and this development implies that Europe is moving toward become a competitor in this whole “Merchants of Death” business:

Washington’s attention is focused on permanent structured co-operation, or Pesco, which is shaping up to be the EU’s most serious attempt yet at forging closer defence ties. Of its 28 member states, 25 have signed up to the scheme that involves 17 projects ranging from improving military mobility to developing a new infantry fighting vehicle.

………

Some Europeans suspect that US reservations are focused less on concerns about Nato than on fears for the US defence industry. “If the EU develops its own fighter aircraft, it won’t need any more Lockheed Martin F-35s,” said one senior MP from Germany’s governing CDU party. “If we really consolidate the European arms industry then it’s that industry that will get the contracts from the EU and that means more competition for US arms exporters.”

(emphasis mine)

Not a surprise, seeing as how the US has basically turned the State Department into the sales arm of the Military Industrial complex.